Regular and intensive use of cannabis and related problems
Dipl.-Psych. Roland Simon
Project:
Regular and intensive use of cannabis and related problems: conceptual framework and data analysis in the EU member states
Final Report
CT.2003.103.P1
Tel. 089 / 360804 - 40
Fax 089 / 360804 - 49 e-mail: simon@ift.de
30.3.2004
D:\726900488.doc 30.3.2004
CONTENTS
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iii
TABLES
Table 1: Global scheme of different aspects of problem cannabis use as discussed
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1 Introduction
1.1 Background
While the early days of the cannabis discussion were dominated by very general positions in relation to use or non-use today more specific questions are discussed. A crucial question in this respect is, which negative consequences might arise from cannabis use (Strang, Witton
& Hall 2000).
The lifetime prevalence of cannabis use in the adult population in the member states of the
European Union is between 20 and 25%, cannabis has been used within a 12 months period by 5 to 10% of the population. For adolescents and young adults the prevalence of cannabis use during the last 12 months is about double as high (EMCDDA 2003). The frequency of use as well as patterns of use vary considerably, as surveys show (e.g. Kraus &
Augustin 2001). Many people use cannabis only during a relatively short period in their lifetime and stop this habit completely afterwards (Perkonigg et al. 1999).
Whenever an intervention is planned for this group, the heterogeneity of cannabis users has to be taken into account. While experimental users of cannabis seldom experience negative consequences of the substance, intensive, regular, long term or dependant use of cannabis can much more often lead to therapeutic needs and types of treatment, which should be tailored accordingly (Steinberg et al. 2002). The subject of this overview are problems related to regular or intensive use of cannabis. The term “problem cannabis use” (PCU) indicate throughout this text, that not experimental, low frequent use of cannabis is the primary interest here, but regular, intensive use of the substance. This use might fulfil the criteria of a “dependence syndrome” (ICD-10, DSM-IV) or “harmful use” (ICD-10) re. “abuse”
(DSM-IV). As there is no simple cutoff between “use” and “problem use” also research on cannabis users in general has been included. In these cases problem drug use has been defined through parameters of intensity or frequency of use.
1.2 The project
This report is the output of a project, which was conducted with the financial support of the
European Monitoring Centre on Drugs and Drug Addiction 1 . Parts of this report are based on the outcome of a recent German study on clients with primary cannabis related problems in outpatient care (“Cannabisbezogene Störungen: Umfang, Behandlungsbedarf und Behandlungsangebot [Cannabis related disorders (CareD): Prevalence, Service needs and
Treatment provision] 2 ). This report was based on the collection of the most relevant recent publications on cannabis, in particular international reviews. This material was complemented with recent publications from the years 2000-2004 and chapter 15 from the
1 Project code CT.2003.103.P1
2 The project was financially supported by the German Ministry of Health and Social Security (BMGS)
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national REITOX reports 2003 produced by the EMDDA National Focal Points in all Member
States and some of the acceding countries.
The following main topics were formulated at the beginning of this project:
regular, intensive or dependent use (=”problem use”) of cannabis
risk factors for PCU
chronic and acute problems correlated with PCU
availability and illegal market
potency of cannabis, THC contents
The outcome of this project should include
Bibliography of the most relevant publications since 1995, given the above mentioned focus of interest
List of the instruments to assess regular/intensive use of cannabis
Framework concept of problematic use of cannabis based on the main elements from the literature
Proposal for future developments needed in research and methodology in order to prepare a more complete and comparable European analysis on problematic cannabis use
1.3 Implementation
The literature search was focused on aspects of negative consequences, patterns
(frequency, duration, onset) and clinical aspects of use (diagnoses). The resulting overview is based on the reviews published more recently by Hall & Room (1995), Kleiber & Kovar
(1998), Hall, Degenhardt, Lynskey (2001), Inserm (2001) and the Ministry of Public Health in
Belgium 2002. In addition more recent publications were searched using the internet via scientific data bases (DIMDI, PubMed) as well as specific information providers in the field
(e.g. www.cannabisschizophrenie.com
). As far as no specific search engines were available www.goole.de
was used with the keywords „cannabis“, „marihuana“ and “marijuana”.
The EMCDDA National Focal Points have as part of their national reports for the year 2003 elaborated a special topic on cannabis. Some of the literature mentioned there has also been included here.
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2 Assessment tools and instruments
Problematic use of cannabis can be assessed either through a specified pattern of use, which can be observed and classified as problematic on the basis of defined cut-off points between problematic and non problematic use as done in chapter 2.1. If a system of classification is used instead, the decision between problematic and non problematic use are made on the basis of weighted parameters on patterns of use, user’s behaviour, and negative consequences or use.
2.1 Assessing problem cannabis use through patterns of use
Problematic use can be defined on the basis of frequency and patterns of use. The cut-off between use and PCU can be defined through a frequency of use during different time periods (lifetime, last year, last 30 days) or the number of consumption days during these periods. Other aspects of the pattern of use (day-time, social setting, working-situation of use) have also been taken as a proxy for PCU in some cases. The EMCDDA model questionnaire includes a question on frequency of use during the last 30 days, which would offer of the elements described.
2.2 Assessing problem cannabis use through clinical aspects of use
PCU can also be defined as dependent or harmful use according to existing systems of classification. Consequences of use, tolerance development, craving and other aspect besides the pattern of use are the basis of such a diagnoses. The key terms here are
“harmful use” and “dependence syndrome” as defined by WHO “International Classification of Diseases”, (Dilling et al. 1999) and “abuse” and “dependence” as defined in the
“Diagnostic and Statististical Manual” (version IV) by the American Psychiatric Association
(APA 1994). While the concept of dependence is very similar in both systems, harmful use and abuse do not correlate very well and are partly based on different definitions and concepts. As Regier at al. (1998) pointed out, even if a diagnosis has been proved reliable and valid, there might be a need to restrict the relevant number of cases to those, which include a “medical necessity” of treatment. This might further reduce the number of cases.
CIDI
An interesting development in this field is the Diagnostic Interview Schedule (DIS). It has been applied within the Epidemiological Catchment Area Study (Regier et al 1990; Regier et al. 1998) and was further developed later into the Composite International Diagnostic
Interview (CIDI) (Robins et al. 1988; Wittchen et al. 1991). The instrument is available in a paper-pencil as well as in an computerised version and covers the most relevant psychiatric diagnoses including substance disorders. It can produce DSM-IV as well as ICD-10 diagnoses. The items of this instrument have been applied in the German national survey on psychoactive substances (Kraus & Augustin 2002) where they offer DSM-IV compatible diagnoses from paper pencil questionnaires filled in by the subjects.
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An international WHO study on the reliability and validity of instruments measuring alcohol and drug use disorders has included the Composite International Diagnostic Interview (CIDI), and a special version of the Alcohol Use Disorder and Associated Disabilities Interview schedule-alcohol/drug-revised (AUDADIS-ADR). Overall the diagnostic concordance coefficients were very good for dependence disorders (0.7-0.9), but were somewhat lower for the abuse and harmful use categories (Ustun et al 1997). An early study on the CIDI
(Wittchen et al. 1991) found good to excellent interrater agreements and kappa values.
CRAFFT
The Car Relax Alone Forget Family or Frinds Troubles (CRAFFT) is a short 5-item test to screen adolescent clinical patients on alcohol related problems as well as on frequent use of alcohol or cannabis. It offers a classification into the categories “any problem” (problem use, abuse, dependence), “any disorder” (abuse, dependence) and “dependence” and shows good psychometric results for general clinical populations (Knight et al. 2002) and in specific ethnic groups. The instrument has been applied successfully with American-Indian and
Alaska-native Americans (Cummins et al. 2003).
CUDIT
Based on the items of the Alcohol Use Disorders Identification Test (AUDIT) (Saunders et al.
1993) a test has been developed for a clinical target group to screen for cannabis abuse or dependence. The Cannabis Use Disorders Identification Test (CUDIT) was found superior to the self-reported frequency of use in a group of out-patient clients with a mild to moderate alcohol dependence. The Diagnostic Interview for Generic Studies (DIGS) was used as criterion (Adamson & Sellman, 2003).
EuropASI
The EuropASI is the European adaptation of the fifth edition of the Addiction Severity Index developed by McLellan and colleges (1985), has been translated into a number of European languages. The complete version has been published by an group of experts (Kokkevi &
Harters 1995). A number of instruments has been developed in different countries for the assessment of clients in clinical settings in addition to that.
Unfortunately, most of the clinical instruments are difficult to apply as part of surveys in the general population due to their size. The application of the EuropASI requires more time than available in most cases as well as skilled interviewers with a considerable degree of clinical experience.
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MECA
The computerised version of NIMH Diagnostic Interview Schedule for Children Version 2.3 was used in the Methods for the Epidemiology of Child and Adolescent Mental Disorders
Study (MECA) for surveys of children and adolescents in an unscreened population-based sample of 7.500 households (Lahey et al 1996). Besides demographic data and information on service needs and utilization substance use as one of several fields has been covered by the diagnostic procedures. The instrument has been described by Shaffer et al. (1996).
SDS
The Severity of Dependence Scale (SDS) has been developed as a short, easily administered scale to measure the degree of dependence on the basis of five items (Gossop et al
1995). The drug user is requested to judge different aspects of craving and loss of control in relation to the substance. The instruments has been developed and validated in five samples of heroin, cocaine and amphetamine users in London and Sidney. This instrument has been developed for a group of highly deviant drug users with frequent i.v. use of hard drugs, cutoffs have been defined for this group. The application of this instrument to primary cannabis users has been tried only recently by Kraus and collegues (publication in preparation).
2.3 Conclusions
For basic analyses and trend information on problem cannabis use subgroups of cannabis users should be defined on the basis of their pattern of use. This can offer a gross estimation of the size of the problem and give some indication on trends.
A more exact and reliable picture of the situation has to include clinical aspects. Most of the instruments described show some short-coming. CRAFFT and CUDIT have been tested only in clinical populations, which might not be sufficient to show their validity and applicability in the general population. EuropASI has been quite successful in clinical research but might be too time consuming for epidemiological research in the population. When PCU is understood in terms of harmful use and dependence CIDI items and CIDI as an computer based instrument for data collection is a promising instrument. They have been applied in a number of studies over the last years and shown good psychometric characteristics. Also promising but less tested is the MECA, which might be a useful instrument especially for children and adolescents.
Further publications on methodological aspects of the assessment of problem cannabis use have been included in the bibliography at the end of this report.
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3 The substance
3.1 Availability and illegal market
Availability and drug use
Availability of drugs and easy access to the substance are crucial factors for all types of psychotropic substances (Mahhadian, Newcomb & Bentler, 1986). Korf (2002) found parallels between the development of availability of cannabis on the Dutch illegal market and the level of consumption in the population. Many factors play a role in this complex system of interactions. The influence of the availability of cannabis on the development of cannabis use is shown by Coffey et al. (2000): In a sample of male pupils in Australia drug using peers and high availability of the drug at the age of 15 correlates with daily use of cannabis at the age of 18.
Availability of drugs can be measured in two ways: perceived availability offers the view of the user while the observation of the illegal market gives a more objective description of the situation. Both ways have been used and both involve certain problems to collect the information in a reliable and valid way.
Perceived availability
Information on perceived availability is part of some of the surveys conducted in EU member states. The answers offer an insight in trends and allow to compare availability for different substances. They do not give, however, an completely objective picture of the situation. Data have been published for example for Germany (Kraus & Augustin 2001). At an European level Eurobarometer (EORG 2002) offers this information. As there is often no indication, how extensive the subject’s personal experiences with purchasing drugs are, the quality of this information is difficult to judge. In some cases it might only reflect the public stereotype on cannabis in the society. Information on drug consumption should be used to check the quality of information on perceived availability.
Drug market
Another way to assess availability of cannabis starts from the drug market. As this is an illegal market, official sales figures are not available and other indicators have to be used instead. Seizures as published by the police or customs count those samples, which have
NOT reached the market. They are therefore only an indirect indicator of the amount of cannabis offered or sold. The total amount cannot be calculated from that figure with an acceptable degree of exactness. However, as on the whole there is little evidence, that the effectiveness of law enforcement has changed very much during the last 10 years all over
Europe, seizures can be taken as an indicator of trends at least.
The positive correlation between perceived availability and the quantity of cannabis-related seizures, which was found in Canada (Smart & Adlaf 1989) shows, that both sources correspondent quite good.
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Other ways to assess availability
Calculations on the basis of production statistics – as done for example for heroin - are not helpful for cannabis, as a considerable percentage of the substance nowadays is produced in-house in Europe. The techniques applied by ONOCP to estimate the heroin production on the basis of the area of poppy cultivation cannot be used in the case of cannabis.
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3.2 Purity
Trends in purity
Purity of cannabis raisin and marihuana has remained rather stable for a long period of time.
At the end of the 80s, Mikuriya and Aldrich (1988) pointed out, that high potency cannabis would have been available already in the 19 th century and found that raisin then had about the same range of THC contents as reported by Perry for 1977: 5-15%. For marihuana the range is given as 2-5%.
Studies indicate since then an increase in THC contents in Europe< (e.g. Bundeskriminalamt
2003) as well as in the United States (ElSohly et al. 2000). An considerable increase in the
THC concentration has been reported within national REITOX reports (e.g. Simon et al.
2002). Compared to Australia (Hall, Degenhardt, Lynskey 2001) the purity of marihuana is higher here and close to hashish (BKA 2001). It has been indicated, that the average purity for the bigger part of the cannabis on the market remained rather stable while an increasing number of high potent samples with an THC contents above 15% or even 25% can be found nowadays. An evaluation of French data for the years 1993 to 2000 point to this conclusion
(Mura et al. 2001).
The considerable increase in the average THC content might be caused through more potent seeds, which have been cultivated over the last 20 years. In-house growing, which can provide perfect growing conditions (light, humidity, water, nutrients), a highly developed industry offering help for growing cannabis (e.g. www.buydutchseeds.com
,) and special journals ( e.g. Hanfblatt in Germany) and helplines for growers like help to optimise cannabis production not only in professional production.
Effects of increased purity
More potent samples of cannabis might increase consumption risks. Possible negative effects could be a faster development of dependence or other negative effects of intensive use of cannabis.
At the moment there is little evidence for that assumption. One useful bit of information concerns the very limited role cannabis oil has played over the last 20 years on the illegal market despite its very high THC content. A comparison of cannabis users in treatment, who were classified due to there pattern of use into low, medium and high risk groups, showed significant differences in the frequency of cannabis consumption but not in the amount of substance used per consumption (Simon & Sonntag, in press). An easy way to increase the amount of THC per consumption would have been to use higher amounts of the substance.
As this did not happen at least in the group under observation, high potent cannabis might not change consumption risks.
A possible positive effect of high potent cannabis is shown by Matthias et al. (1997), who compared the tar delivery through one cannabis cigarette, using THC contents between 0 and 3,95%. They found a lower tar intake with the high potent substance for some of the subjects, which they explain by a reduced intake of smoke.
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Research on the pharmacokinetics of cannabinol showed in a group of six men a systemic availability of THC from 6 to 65%. This high variability underlines, that THC contents is only one of many factors, which influences the strength of effects (Johansson et al. 1987). Even if users would prefer stronger effects, high potent sorts could not produce automatically strong effects.
An analysis of drug seizures made in an region of Denmark in 1992 and 1993 also found a great variation of purity for all drugs examined and stated, that it would be difficult for the user to obtain the same quality of a substance each time (Kaa & Bowman, 1998).
On the whole there is no empirical evidence that the availability of high potent cannabis has changed the pattern of use in a problematic way. It might, however, have epidemiological effects which are not visible yet.
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4 Problematic use of cannabis
Antecedent and consequent factors are discussed in the following chapters. The first one is seen as a possible cause or contributing factor for the development of PCU, the latter as an effect or consequence of the drug using behaviour. Doing this, it should be kept in mind, that such an distinction can not always be made. Problematic situation in the family of origin or school problems which might have been contributing factors for PCU can further develop and become even more problematic after PCU started. As making the distinction between antecedence and consequence helps to organise this report it has been done despite the problems described above.
The overview on contributing factors and effects has been organised on the basis of the distinction between short-term/acute and long-term/chronic effects and the question, if these effects would apply to the user or the social environment around him.
Table 1: Global scheme of different aspects of problem cannabis use as discussed in this report
Aspects
Antecedents
Acute effects
Chronic effects
Secondary effects
User
Use of psychotropic substances
Mental disorder
Somatic
Mental
Somatic
Mental
4.1.3
4.1.4
4.2.2
4.2.3
Subject
Social environment
Demographic factors 4.1.1
Family, social situation 4.1.2
4.3.2
4.3.3
Children
Adaptation
Traffic accidents
Crime
4.4.1
4.4.2
4.4.3
4.4.4
Attached: number of chapters in this report, where the topics are discussed
4.1 Antecedents of problem cannabis use
Research carried out in Europe, the US, Australia and New Zealand, found a number of individual factors correlating with the occurrence of problematic consumption of cannabis.
However, we have to point out that the available list of possible risk factors has to be regarded as preliminary (Höfler et al. 1999) and that the links are complex. Küfner et al.
(1999) have summarized various risk factors, but many of the associations found between client characteristics or behaviour and PCU are only significant until aspects of social and personal situation, family of origin or socio-economic status are taken into consideration as covariates (Inserm 2001).
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4.1.1 Demographic factors
On the whole there is a higher risk for men to develop problematic use of cannabis (Höfler et al. 1999). This applies to most psychoactive substances. According to a Swiss survey experience with cannabis correlates positively with the level of education, but frequency of use (as an indicator of PCU) shows the opposite patters: the higher the level of education the lower the frequency of use. The percentage of daily users is almost three times (12,9%) as high among people with low education than among people with high education
(Fahrenkrug, Müller R., Müller S. 2001).
4.1.2 Family background and social situation
Family factors are highly important (Inserm 2001). Negative effects were found for drug use of the mother (Kleiber & Soellner 1998) as well as alcohol problems of the mother (Duwe,
Schumann, Küfner 2001). In an US national household sample (N= 4.023; 12 - 17 years) sexual assault and being a witness of violence correlates with an increased risk of substance abuse/ dependence. A study in Norway found, that interrupted education or living with only one or none of the parents correlates with more extensive use of cannabis (Pedersen 1998).
Especially during adolescence peers have a strong influence. This applies to the consumption of cannabis (Inserm 2001), where peer groups seem to influence consumption behaviour of their members and cannot been see only as gathering together on the base of priori common interests in drugs. For the development of PCU, however, peer group effects are significantly lower (Shedler & Block 1990, Höfler et al. 1999).
When discussing the role of the peers we have to keep in mind, that they are not chosen by chance and that the peer group is not developing by chance, but young people join together because they share certain characters, targets and values. To a certain extent they are thus making their choice, what influences they will be exposed to.
In special settings, for instance in youth clubs, the rate of PCU is significantly increased
(Brandstetter & Kuntsche 2001). Corr (1999) reports 35% of current cannabis users in a sample of homeless people, Torres & Gomes (2002) finds 38,7% of recent users amongst prison inmates. These are selective, partly highly deviating groups who differ by a number of characteristics from the average population. An increased risk to develop problematic cannabis use always can be explained at least to a certain degree on the basis of these factors.
In a sample of pupils in Australia males who had drug using peers at the age of 15 showed an increased risk of PCU at 18. For females high-dose alcohol use and antisocial behaviour at 15 increased the risk of PCU at 18. For both cigarette smoking is an important predictor
(Coffey et al. 2000).
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4.1.3 Use of other psychotropic substances
The use and - even more – PCU is correlated with the consumption of legal psychotropic substances. Drinking alcohol and smoking tobacco before the age of 14 as well as getting drunk (for the first) time under the age of 14 is associated with the development of a problematic cannabis use later (Duwe, Schumann, Küfner 2001). Höfler et al. (1999) point out that also nicotine addiction has to be considered as a risk factor, while biosocial indicators do not have any predictive value.
Usually cannabis is the first – and often the only – illegal drug used. When other drugs are used in addition to that, the risk of addiction is increased and regular use is more frequent
(Kleiber & Soellner 1998).
4.1.4 Mental disorders and problems
Whereas experimental use of cannabis for young people correlates positively with social conformity, PCU can be found more often among young people with personality and social behaviour disorders (Shedler & Block 1990). Psychopathological effects can often be visible before the beginning of drug use (Kessler et al. 2001). Behavioural or conduct disorders during childhood, for instance committing robberies, truancy or falsifying signatures (Duwe,
Schumann, Küfner 2001), have predictive value for later drug use, especially by female consumers. Whereas affective disorders do not appear frequently during past history, the risk of later PCU is increased by ADHD (Höfler et al. 1999). Kessler et al. (2001) show that early psychological disorders are valid predictions not only for drug use but above all for problematic or addictive use. This study does not specially apply to cannabis but to drug use in general.
4.2 Acute Effects
4.2.1 Overview
The acute effect of cannabis varies considerably within and between individuals.
Inexperienced users often do not feel any effect. Only in few cases this effect is felt to be unpleasant (Schumann et al. 2000). Johnson (1990) points out that the experienced effect consists of an interaction between consumed quantity, the amount of active substance in it
(=purity), the mode of consumption (smoking or eating), and individual expectations and social situation. Besides the chemical substance (drug) the consumer’s expectations (set) as well as the social surrounding in which consumption takes place (setting) have an impact on the effect (Zinberg 1984).
In many cases not only intensity but also the direction of effects may vary. Thus cannabis, which in usually relaxing and relieving fear, can also cause fear and panic attacks even for the same person. Effects on blood pressure may also vary – dependent on the body’s position, sitting or lying – between decrease and increase.
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4.2.2 Somatic effects
Intoxication
Toxicity of cannabis and its most important active substance THC is low. By far the majority of sources state that deaths in connection with an overdose of cannabis have not been proven until today (Kleiber & Kovar 1997; van Laar et al. 2003). A Swedish study, which found over 5 years 71 deaths related to cannabis but no other illegal drug, is rather unique
(Fugelstad et al. 1998). A clue on the frequency of severe physical acute problems caused by cannabis is provided by the statistics of emergency cases in Amsterdam for the year
2001. On the whole 243 persons were registered as emergency cases because of cannabis.
Given the rather high prevalence of cannabis use in Amsterdam, this is a relatively low figure.
Mortality
A Swedish study carried out among military conscripts found a higher mortality at a later date amongst persons with increased cannabis consumption at the time of their medical examination. However, this association was reduced considerably by taking into consideration several mediating variables: later use of more severe drugs after, getting in touch with police for several times, increased alcohol consumption, and early psychiatric diagnosis. These parameters showed a correlation with increased cannabis use on one hand and an increased mortality at a l ater time on the other hand (Andréasson & Allebeck 1990).
According to other studies increased mortality due to HIV/ AIDS (Hall & Solowij 1998) is another mediating factor between cannabis use and mortality. When correcting the variables for risk behaviour and homosexuality as a risk factor for HIV-infections, this association is not longer significant (Sidney et al. 1997).
In total it can be stated, that there is nearly no evidence, that cannabis as a substance increases mortality. However, there is an association between cannabis use and behaviours which are linked to corresponding risks.
Cardiovascular effects
THC, the main psychotropic substance in cannabis, influences heart beat and blood pressure. Frequently it causes tachycardia and blood pressure can decrease or increase - depending on a sitting or standing position and tolerance – which can causes in some cases intense dizziness (Hall & Solowij 1998; Kleiber & Kovar 1997). Adams & Martin (1969) found brachycardia and hypertension also in animal models. Given this evidence, Hall & Room
(1995) point out, that cannabis consumption could be problematic for people suffering from a cardiovascular disease and Hollister (1998) considers cannabis use as risky mainly for older people of weak health. The age distribution of cannabis use shows a very small prevalence in this age group, however.
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Respiratory system
Wu et al. (1988) found after smoking cannabis five times as much carboxyhemoglobin in the blood and three times as much tar in the smoke compared to tobacco. 1/3 more tar remains in the respiratory tract because cannabis smokers breath deeper and inhale longer.
Psychomotor effects
Cannabis reduces performance of short-term memory, concentration, attention, and psychomotor coordination. Hall & Solowij (1998) report about effects in laboratory experiments corresponding to an alcohol intoxication of about 0,7-1,0 pro mille. The extent of this effect may, however, vary considerably. For more details please see chapter 4.4.
Other somatic effects
Consumption of cannabis may cause sickness and vomiting in some cases (Berke & Hernton
1974), but an increased appetite is a typical short-term effect of cannabis intoxication. More frequent dryness of eyes and mouth, cough and impaired balance are found (Kleiber &
Soellner 1998). All these effects are in general light to moderate.
4.2.3 Mental effects
The most frequent acute psychological effects of cannabis use are euphoria and feeling well at first, which are followed by sedative effects depending on the dosage. Changes in perception (colours, time, space) as well as even hallucinations may appear (Hollister 1986) and in addition the following impairments of mental functioning have been found as negative effects..
Cognition
The effects of cannabis, which have been described as similar to an alcohol level of 0,7-1,0 pro mille, reduce cognitive performance in general. Especially the ability to concentrate and attention span as well and short-term memory are reduced, which has negative impact on performance in school and working place (Kleiber & Kovar 1997, Tennent & Groesbeck
1972, Hall & Room 1995, Hall & Solowij 1998)
Dysphoria, anxiety and panic disorders
The anxiety relieving and sedative effects of cannabis can also turn into the opposite. Selfreports of cannabis users in New Zealand showed that 14% of the men and 30% of the women experienced panic attacks after using cannabis (Thomas 1996). Negative effects on mood (dysphoria) (Berke & Hernton; Hall & Solowij 1998; Hall & Room 1995) and anxiety as well as panic attacks were reported by a number of sources (Berke & Hernton 1974; Hall &
Solowij 1998). It seems that experienced consumers are able to deal better with these negative effects (Berke & Hernton 1974; Hall & Room 1995), however the risk remains about the same that they might occur after cannabis use. Women are more frequently affected by these negative effects (Thomas 1996).
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Toxic psychoses
Sudden relapses into a state resembling an acute cannabis intoxication without having used cannabis („Flashbacks“) have been reported in individual cases but there is neither a clear description nor reliable figures about the frequency of this phenomenon. On the whole it seems that such effects are more frequent when using hallucinogens and temporal in any case (Tennent & Groesbeck 1972). Consumers of cannabis may have psychotic states in the course of intoxication, especially under very high dosages (Tennent & Groesbeck 1972). A research study amongst recruits in the German Army found, that the number of persons discharged from military service because of psychotic disorders doubled between 1988 and
1992 (Wimmer & Mahlberg 1996). Similar developments were found among American soldiers in Germany earlier, where an increase in the number of schizophrenic reactions followed a significant increase of drug use in this population. However, in these cases the persons consumed many different drugs and effects cannot be seen in connection with cannabis use only (Tennent & Groesbeck 1972).
The concept “cannabis psychosis” is not used today any longer by many experts as they argue, that this pattern of symptoms can be described adequately through “toxic psychosis” without defining an additional diagnosis. This state is caused in most cases by consumption of medium up to high doses of cannabis (Thornicroft 1990).
4.3 Chronic Effects
4.3.1 Overview
It is difficult to record long-term effects of cannabis use. A number of animal experiments showed such effects but can serve only as a model and inform about possible risks (Adams
& Martin 1996). In many cases there is a lack of human studies, in other cases the effect of cannabis use can hardly be separated from effect though tobacco or other drugs. As cannabis is often used mixed with tobacco, the negative effects of tobacco smoking are also always involved.
In the following chapter effects are described which are very likely caused by cannabis use due to present knowledge. For a general survey of research results especially see Kleiber &
Kovar (1997) and Inserm (2001). Although cannabis users exhibit some negative deviations and additional health risks in comparison to the remaining population, they make hardly more demands to the healthcare system (Hollister 1998). Even long-term cannabis users do not report more health problems than a control group (Coggan et al. 2002).
4.3.2 Somatic effects
Respiratory system
One of the most important risks concern damages to the lungs and respiratory tracts (Hall &
Room 1995). Acute effects in this are hoarseness etc. The effects of cannabis on breathing constitute acute risks for asthmatics (Hall & Room 1995). A chronic damage to the bronchial tubes is associated to the use of cannabis as well as a reduced function of the lungs (Hall &
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Solowij 1998, Inserm 2001). In animal experiments carcinogenic effects of cannabis smoke were proved, but the clinical relevance of these results could not yet be shown in human studies(Hall & Solowij 1998).
Comparing the composition of tobacco smoke and cannabis smoke, similar effects especially in relation to the development of lung and gullet cancer can be expected. There seem to be a higher risk compared to tobacco only as cannabis is burning under higher temperatures and is inhaled more deep that tobacco (Hall & Solowij 1998).
Wu et al. (1988) found after smoking cannabis five times as much carboxyhemoglobin in the blood and three times as much tar in the smoke compared to tobacco. 1/3 more tar remains in the respiratory tract because cannabis smokers breath deeper and inhale longer.
However, the number of joints smoked per day is considerably below the number of tobacco cigarettes smoked for most people, which again reduces the total effect of cannabis. THC as active substance in cannabis has practically no influence on these negative effects, which are rather exclusively caused by burning the additional substances included in cannabis or marihuana.
Reproduction
Negative effects on the reproduction system have been proved up till now only in animal experiments (Hall & Room 1995). Early results concerning restriction of the number of sperms of men have not been confirmed.
Other somatic effects
Suppressed functioning of the immune system through THC were proved in animal experiments, but there are no valid results from human studies (Hall & Room 1995).
Neurological damages caused by cannabis were found in an early study (Campbell 1971), but also were never replicated.
4.3.3 Mental effects
In a German study (Kleiber & Soellner 1998) more than 20% of the cannabis users reported repeated psychological problems linked to cannabis consumption. Hollister (1998) and Hall &
Solowij (1997) describe different aspects of mental health and risks connected with cannabis.
Apart from possible effects of cannabis on mental basic abilities, especially addiction and harmful use/ abuse are relevant here. Tolerance development here and psychological consequences for systematic reasons are discussed in this place.
Correlations between global mental health status and cannabis use have been found by
McGee at al. (2002). In a longitudinal study in New Zealand (Dunedin Multidisciplinary Health and Development Study) mental disorders at the age of 15 were followed by a small, but significant increase in cannabis use at 18; cannabis use at 18 was positively correlated to mental health problems at the age of 21.
16
Poikolainen et al. (2001) and Smit, Bolier and Cuijpers (2003) draw from their research the conclusion, that it would be more likely, that cannabis use causes mental health problems than being a consequence of such problems.
An increased rate of coexisting psychiatric disorders was found for current users of all illegal substances compared to nonusers also in the “Methods for the Epidemiology of Child and
Adolescent Mental Disorders (MECA)” study. Especially the mood disorders and disruptive behaviour disorders were much more frequent in this group. Cannabis plays a major role in this group, but its effects have not been analysed separately (Kandel et al. 1999).
Based on a national mental health survey on children, a number of 2.624 subjects between
13 and 15 years were included in a study on the relation between psychotropic substance use and global psychiatric morbidity. The strongest correlation was found for regular tobacco smoking, a smaller effect for regular cannabis use (Boys et al. 2003).
In the Epidemiologic Catchment Area (ECA) Study, which was conducted in an US population (N=20,291) 50,1% of all persons with a lifetime prevalence of cannabis abuse show mental disorders (substance abused not included) during their lifetime (Regier et al.,
1990). Narrow, Robins and Regier (2002) request to look for the clinical significance of diagnoses of mental disorders which are produced following the standards at hand. When using demands for professional help or medication as an indication that a disorder really interferes with the drug user’s daily life, the prevalence or mental health disorders amongst the above mentioned problem cannabis users in the Epidemiological Catchment Area (ECA) study is reduced to 17%, in the National Comorbidity Survey (NCS) to 32%.
Cognition
Acute negative effects of cannabis on the performance of short-term memory, concentration and other aspects cognitive performance are well documented (Tennent & Groesbeck 1972,
Hall & Room 1995, Hall & Solowij 1998). The question is still under discussion, if these effects are permanent. In animal experiments performance was reduced after cannabis use for up to 3 weeks and changes of the EEG were found during long-term use (Adams & Martin
1996). On the other side a number of studies presume that up till now there is no sufficient evidence that cannabis use causes a permanent reduction of cognitive performances. Subtle reductions may occur which could be measured only with more suitable instruments
(Hollister 1998). Research on this topic is difficult as there is a correlation between intensity of consumption and acute effect on cognitive performances as well as after-effects of cannabis use which can last for more than 24 hours.
Results from an American survey among students in 140 colleges show a relationship between (bad) marks and cannabis use. However, these users were beside there drug use also more interested in “binge drinking”, smoking tobacco and changing sexual partners, which might also indicate differences in their motivation of performance. Also for this reason it has not been proven that cannabis is the reason for the defects (Bell, Wechsler, Johnston
1997).
17
Sabroe and Fonager (2002) found a negative association between cannabis use and school performance in Denmark, which might be caused by reduced ability to concentrate as it has been found in another study (van der Poel et al 1999).
The negative effect might depend on the dosage. Tennent & Groesbeck (1972) found in a study carried out among American soldiers in Germany that consuming up to 12 grams of cannabis per month caused hardly any negative effects while consumption of alcohol correlated with disorders in the fields of concentration, memory and judgement.
The same conclusion can be drawn from the study of Pencer and Addington (2003), who found no significant correlation between cognitive disorders and light up to mediocre cannabis use for mentally ill persons.
Comparing IQs, which were assessed at the age of 9 to 12 years and again 8 years later, a decrease of (on the average) 4.1 points was found for persons, who were smoking cannabis at least five times per week at the time of the second assessment. All other groups including light users and former users of cannabis show an increase in IQ points over the same time period. The authors draw the conclusion, that cannabis had no long term negative effect on global intelligence but negative short term effects (Fried, Watkinson & Gray, 2002).
A meta-analysis by Grant et al. (2003) show, that differences in cognitive functioning between users and nonusers a no longer significant after users have gone though an abstinence period of a minimum of 3 weeks.
Development
Cannabis use is especially popular among young people (von Sydow et al. 2001). This stage of life is of special importance for personal development. It is marked by trial and error and testing the own limits. Drug use – particularly the consumption of cannabis – is one aspect of this risk behaviour. Shedler and Block (1990) show, that experimenting with cannabis is rather a sign of mental health at that age. However, this does not apply to regular and frequent use, which can cause or intensify problems.
Cannabis use is associated with a higher rate of school dropout (Hall & Solowij 1998) as well as the consumer’s entry into the drug scene (Lynsksy 2003). A number of confounding variables play a role here and Hall & Solowij (1997) do not confirm an negative effect of cannabis use on psychosocial development as such. Cannabis use is not very much the reason for a number of problems but works as an amplifier of such problems. Forming groups with other cannabis users may intensify the already existing non-conformism. Already existing conduct and behavioural problems in early childhood and early use of legal substances etc. may worsen the problem situation by choosing a corresponding peer-group and obstruct the development of personality (Hall & Room 1995; Brandstetter & Kuntsche 2001).
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Depression and suicide
As a consequence of cannabis use also depressive disorders may occur. Inserm (2001) point out that there is an increased risk for suicide among consumers of cannabis. However, the substance may not be the only cause, but again is interconnected with a number of succeeding behaviours (use of hard drugs, intravenous drug use) which are increasing the risk of suicide. Patton and colleagues (2002) found in a longitudinal survey carried out for a period of 7 years among an Australian cohort of pupils in secondary schools (N=1601), that using cannabis at least once a week for girls doubled the risk of developing depression or anxieties after 6 years. Daily use of cannabis is linked to a fivefold higher probability. The opposite sequence – cannabis use following depression or anxiety disorders - showed no significant effect, which support a causal role of cannabis use (Patton et al. 2002).
In a longitudinal survey, Bovasso (2001) also found a correlation between cannabis use and depression. For persons without depressive symptoms the risk to show symptoms of depression after 15 years were about four times as high when they were cannabis users compared to non-users. Factors like age, sex, antisocial personality and others have been used as covariates.
Jääskeläinen (2003) and Poikolainen (2002) conclude from their studies, that cannabis use make persons more liable for depression. Fergusson and Horwood(1987) indicate that
Persons with cannabis abuse or addiction are also more affected by other psychiatric disorders in general.
Schizophrenia
One of the main points of discussion in relation to cannabis risks are psychotic and schizophrenic disorders. An epidemiological longitudinal study among army conscripts in
Sweden found an increased risk of schizophrenic disorders for cannabis users 15 years after the time of medical examination (Andréasson et al. 1987, Allebeck, Adamsson, Engström
1993). The relative risk is 6.0% for persons having used cannabis more than fifty times.
There was no former diagnosis of psychological disorders before starting cannabis use, but it cannot be excluded that the substance is used as self-medication for a beginning schizophrenia. An up-to-date analysis using data on schizophrenic diseases in the Swedish register up to the year 1996 found a relative risk of 6.7%. When cases of schizophrenic disorders appearing within 5 years after medical examination are excluded to guarantee the chronological sequence between cannabis use and psychological disorder, the results were similar (Zammit et al. 2002). While schizophrenic disorders are as frequent in families of cannabis users and of nonusers, negative social conditions are more frequent in users’ families. Johnson, Smith, Taylor (1988) object, that many of the subjects in this study used amphetamines in addition to cannabis. The known psychotic effects of this substance might be diagnosed erroneously as schizophrenia.
A recent longitudinal study (Arsenault et al. 2002) could show by means of a relatively small population that cannabis use in the age of 15 respectively 18 years increases the probability
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of schizophrenic disorders at the age of 26 even if pre-existing psychosis was controlled for.
An earlier use showed more significant effects.
In a Canadian study a random survey among an adult population out of 2144 households found a lifetime prevalence of 8.0% abuse or addiction of drugs and of 0.7% for schizophrenia. The lifetime prevalence of drug abuse and addiction was 50.8% among this group and thus about 6 times as high as among the entire population. Although this study does not report explicitly effects of cannabis, the high availability of cannabis as well as the high affinity of schizophrenic people for this substance give rise to the suspicion that extensively cannabis was concerned (Bland, Newman & Orn 1986).
In a high-risk-group of persons with subliminal psychotic symptoms or a high burden of relatives with such disorders, cannabis consumption or cannabis addiction does not increase the risk for developing psychosis during a period of 24 months (Phillips et al. 2002).
Dixon and collegues (1990) point out that cannabis effects might be interesting for persons people with schizophrenic disorders to calm down disagreeable sensations. Because of the anti-depressive and sedative effects cannabis might be preferred to alcohol, cocaine or opiates (Schneider & Siris 1987). The “socialising effect” which helps to reduce the distance to social environment is also considered as positive (Dixon et al. 1990).
When analysing the clinical populations of schizophrenic patients, users of cannabis show an earlier outbreak, but no differences in family anamnesis, pre-morbid social development, outcome (Eikmeiner et al. 1991) or neuro-cognitive effects (Cleghorn 1991). Other studies found only small differences between cannabis users and non-users in a clinical population
(Dixon et al. 1990).
A crucial question is, whether cannabis causes schizophrenic phases or if can only trigger them on the basis of an existing vulnerability. Hall & Room (1995) assume that the latter is the case and that cannabis use worsens the course of development after the outbreak. If cannabis causes schizophrenia or increases positive symptoms, the total effect must be relatively small as the strong increase of cannabis use in the population in Western societies during the last decades has not produced a visible increase in the prevalence of psychosis in the population (Hall & Solowij 1997). Only some examples are known: an increase of psychotic disorders – however not specifically for individual drugs – took place parallel to a significantly increase of drug use in the US army in Germany (Tennent & Groesbeck 1972);
Kay (1992) points out that people from the Dominican Republic resident in Great Britain as well as in their home country show rates of schizophrenic disorders (11.8/1000) which are 6 to 8 fold to the British population. In the African countries of origin of their genotype there is no increased rate of schizophrenic disorders to be found. The authors conclude, that the intense use of cannabis in this population may be a reason for the increased rate of schizophrenic disorders. Similar experiences have also been reported from the former
French colonies.
The substance can increase to a certain extent the symptoms of psychosis (Hall & Solowij
1998). Long-term use is correlated with worse conformity and more addiction problems in the family (Caspari 1998). Relapses into psychotic states happen more frequent and earlier
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among cannabis users (Linszen, Dingemans & Lenior 1 994). Häfner and collegues (Häfner et al. 2002) examined the chronological sequences of consumption and schizophrenic symptoms of a group of persons with first schizophrenic periods of illness and found indications that cannabis should rather to be regarded as unsuitable attempt of selfmedication than as a trigger.
Pirkola (2003) draw the conclusion, that cannabis increases the risk of schizophrenia for its users, but still feel that genetic factors have a bigger influence in this development.
In a Dutch survey cannabis use is correlated with an increased number of psychiatric symptoms and the respective need for treatment three years. These results show, that cannabis can cause psychotic effects as well as worsen exiting ones, if a vulnerability is given (van Os et al. 2002).
A meta-analysis published recently (Arseneault et al. 2004) comes to the conclusions on the basis of five methodological sound studies, that cannabis use can be seen as a risk factor for the development of psychotic disorders especially for vulnerable youths. At individual and social level, the authors concluded, incidence of schizophrenia could be reduced by avoiding the cannabis use.
Taking together all these results, the conclusions made by Hall und Degenhardt (2000) are very reasonable: the link between cannabis and schizophrenia is not yet clear, but there is a growing bulk of research indicating that cannabis worsens symptoms of an existing schizophrenia and that it can trigger psychotic disorders when a certain vulneratbility is there.
Tolerance syndrome, harmful use and addiction
The development of tolerance towards THC is evident for intense, longer-term use of cannabis as animal models and human research studies show (Adams & Martin 1996). The degree of addiction seems to be not very strong as in animal experiments cannabis has only little power as a reinforcer and significantly less medical help is necessary for withdrawal from cannabis than for instance from heroin.
A representative epidemiological study in Germany found a lifetime prevalence (DSM-IV) of
5.5% for cannabis abuse (Lieb et al. 2000, von Sydow et al. 2001) in the age-group 14-24.
This group showed a stable pattern of use during an observation period of 4 years. A longitudinal study in New Zealand showed 7.3% for the age group between 16 and 18 years
(Fergusson & Horwood 1997).
Cannabis dependence as a concept contains several critical aspects: preoccupation with the substance, compulsive use and relapse or recurrent use (Miller & Gold 1989). Continuous use despite significant negative consequences can give a first indication of dependence as defomed above (Reynaud & Schwan, 2003).
There are in fact cases of cannabis addiction (Hall & Solowij 1997) and Hall & Room (1995) consider this disorder even as one of the most frequent addictions in Western societies.
According to estimations in the United States 10% of intensive cannabis users become addicted in the course of their life. The same figures for alcohol (15%), nicotine (32%) and
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opiates (23%) indicate, that there is a comparatively low risk of becoming dependent on cannabis (Hall & Solowij 1998). In Germany in the age group 14 to 24 a lifetime-prevalence of cannabis addiction of 2.2% was found (von Sydow et al. 2001). In the US a rate of 2.6% was found for the age group 12 to 17, 3.5% for the group 18 to 25 (Dennis et al. 2002). In
New Zealand 4.3% of the age group between 16 and 18 fulfil the criteria of addiction in the age between 16 and 18 (Fergusson & Horwood 1997).
Withdrawal symptoms as well as the wish to reduce respectively control consumption are the most frequent DSM-VI criteria found for these cases (Kleiber & Soellner 1998). There is a positive correlation of addiction with intensity of use, but not with duration of use (Kleiber &
Soellner 1998). The drug user’s subjective feeling of being addicted to the substance correlates with DSM-IV diagnoses but is more critical than that.
In an American sample a critical value of 3 out of 7 criteria for addiction (similar to ICD-10) was exceeded by 28% of current cannabis users. Among them persons at the age of 12 to
17 years are more often affected (43%) than persons above 25 (18%) (Dennis et al. 2002).
In an experimental setting, withdrawal symptoms during a 45 days abstinence phase were studied amongst 18 subjects. All of them were regular cannabis users (on the average for
12.8 years) and used cannabis nearly daily before the study started. Withdrawal symptoms found are aggression, anger, anxiety, decreased appetite, irritability, sleep problems and others. They start 1-3 days after the start of abstinence, peak between day 2 and 6, most effects last 4-14 days. Over 75% of the subjects experience at least four symptoms.
Magnitude and time course of effects are similar to tobacco (Budney et al. 2003).
Use of other psychotropic substances
The „stepping-stone“ theory, that cannabis use will be followed automatically by other more risky drugs, is not supported by facts and not taken as valid also in the drug discussion.
Nevertheless the cannabis use is linked to an increased risk of using other psychotropic substances as well.
A study amongst 311 monozygotic and dizygotic same-sex twins in Australia examines the correlation between use of psychotropic substances before the age of 17 years and later drug use and dependence. Early use of cannabis is associated with a higher risk of developing alcohol dependence or drug abuse/dependence (odds: 2.1 to 5.2) compared to non-using co-twins. Controlling for known risk factors these results remain stable. The authors conclude, that effects of early cannabis use on later drug use and alcohol dependence go beyond genetic or shared environmental factors.
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4.4 Secondary Effects
4.4.1 Effects to unborn children
Children of mothers consuming cannabis show a slightly reduced birth-weight (Hall & Room
1995). Hollister (1998) is quoting Zuckerman et al. (1989) who also found that children of mothers smoking marihuana were born smaller and lighter and had smaller heads.
Children of cannabis using mothers might show some cognitive impairment. Hall & Solowij
(1998) mention temporary restrictions in early childhood. In the Ottawa Prenatal Prospective
Study (Fried 1993) offspring of cannabis using mothers showed no effects at the age of one year as well as at the age of five to six years, when the effect of confounding variables is excluded. Measurement at the age of four years showed reduced performance in memory and verbalization but it has to be mentioned that the relationship between cannabis use of the mother and child characteristics can be mediated by other factors. For instance a reduced parental engagement of the mother (Fischer et al. 2001), but also the use of other psychotropic substances may play a part as confounding variable.
Performance and social adaptation
Concentration, short-term memory, speed of reaction and power of judgement are considerably reduced during cannabis intoxication (Kleiber & Kovar 1997). There is a significant association between cannabis use and problems of social adaptation, problems in school and at the workplace (Fergusson & Horwood 1997), school performance (Inserm
2001; Kandel & Davies 1996), work performance (Kandel & Davies 1996; Thomas 1996) and general social problems (Thomas 1996). Cannabis users have more family problems (Kandel
& Davies 1996). In addition to problems of concentration and general cognitive impairment cannabis can have an negative impact on school education through increased risk of leaving school without qualification or failure to enter university or to obtain a degree (Fergusson,
Horwood & Beautrais 2003).
Presumably many activities in school or profession cannot be carried out adequately in the state of intoxication. There is a high probability that the speed of work as well as the quality of its results is decreased by the reduced performance of the drug user. Studies carried out in Greece (Stefanis 1977) and Jamaica (Rubin 1975) nearly 30 years ago found no problems for chronic cannabis consumers to live inconspicuously and integrated into the working society. It can be argued, that working conditions today might produce more problems for drug users in everyday life. In this respect a loss of productivity is assumed, but has not been confirmed by corresponding studies or estimations (Hall & Room 1995).
In the study of Shedler & Block (1990) intensive use of cannabis is correlated with a clear deterioration of interpersonal relationship and perceived stress. The link between cannabis use and social consequences weakens when other factors are included in the analysis
(Kleiber & Soellner 1998). As Hall & Solowij (1997) point out, early contact with Cannabis increase the risk of using heroin or cocaine later, which should not support the “steppingstone”-hypothesis (Hall & Solowij 1998), but make clear, that these are only correlations.
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On the whole there seem to be a correlation between the amount problems in everyday life and cannabis use (The National Board of Health and the Danish Cancer Society 2003).
4.4.2 Traffic accidents
A cannabis level of 7 – 15 ng/ml blood corresponding to 1 joint of 10 – 15 mg THC causes critical effects on the driving performance one hour after consumption (Schulz et al. 1998).
The typical effect of one cannabis cigarette has been is compared to an alcohol level of 0.5-
1.0 pro mille (Hall & Room 1995). The acute effects disappear after 24 hours at the latest
(Kleiber & Kovar 1997) but signs of reduced cognitive functioning have been found up to 3 weeks after cannabis use.
Effects on the fitness for flying of pilots could be testified up to 24 hours (Hollister 1998). An estimation of the effects is difficult as the substance, the mode of consumption and individual reactions may vary considerably (Schulz et al. 1998). Moreover, consumers of cannabis sometimes overestimate their state of being “high” and compensate a part of the restrictions by driving more slowly and carefully. In contrast to persons driving under the influence of alcohol the style of driving does not become more aggressive but more defensive (Adams &
Martin 1996). Under experimental conditions clear negative effects on driving have been found (Lagier et al. 1996, Mura 1999). In everyday life the risk of accident for this group is only slightly increased (Ramakers et al. in press), what might be due to a more cautious way of driving while intoxicated (Sexton et al. 2000). The risks increase considerably if cannabis and alcohol use are combined (Inserm 2001, Vollrath et al. 2001).
When comparing different substances in statistical data about accidents and persons causing accidents show that the risks by car drivers being intoxicated with cannabis are comparatively lower than by persons intoxicated with other psychotropic substances including alcohol (Inserm 2001). In a “roadside survey” investigating a representative sample of car drivers who have been tested on the spot for different substances, cannabis could be proved for 0,57% of the tested drivers and alcohol for 5.48%. The respective values for opiates were 0.15-0.62% (heroin, codeine). Only one out of 2017 samples showed cannabis in an amount (> 40 ng/ml), indicating an acute reduction of performance (Krüger, Schulz &
Magerl 1998).
The association between the risk of traffic accidents and cannabis using behavior has been examined in a longitudinal study over a period of three years. There was an association found between cannabis use and ‘active’ traffic accidents, where the person contributed to the accident. This link, however, seems to be mainly a consequence of differences in risk behavior and personal characteristics (e.g. gender) between cannabis users and non-users.
(Fergusson & Horwood, 2001)
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4.4.3 Crime
Violent crime under the influence of cannabis is rare. The sedative effect which follows soon after consumption is rather opposing aggressive behaviours than intensifying or producing them. Thus – in contrast to cocaine, crack or alcohol - cannabis does usually not increase violent offences in different situations (Berke & Hernton 1974).
Cannabis use is one of several problem behaviours, which are found frequently amongst adolescents. Jessor and Jessor (1977) have developed the concept of a “syndrome” of problematic behaviour, where a cause-effect relationship is difficult to find. Farrell et al.
(1992) shows for 7 th and 9 th grade school children a high correlation between different types of behaviour, which are perceived as problematic by their environment: smoking cigarettes, drinking alcohol and marijuana, delinquency, early sexual intercourse. These results were found at American urban schools, where the majority of children came from low-income
African American families. Generalisation of results to other settings might not be adequate.
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5 The main conceptual elements
A number of studies has found empirical evidence for risks of problem cannabis use (PCU) and negative consequences of it. The following tables give an overview on the most important aspects of PCU. They are based on the results reported in chapter four, the literature can be found in the annex of this report. The selection of factors described here is based on the research outcome available. You could think of many more variables as risk factors for the development of PCU or as negative consequences of cannabis use. The selection shown here follows empirical evidence available when this report has been prepared. As research will continue, new risk factors and negative consequences might become visible in future and the risks linked to cannabis may be perceived in a different way. The overview given here should be seen as a snap-shot of the evidence available today.
5.1 Antecedent factors of problem cannabis use
Antecedent factors of problem cannabis use have been found in the field of demography.
Being male or reaching only a low level of school education is associated with an increased risk of PCU. Early and intensive use of legal psychotropic substances, childhood mental disorders and conduct disorders also mean increased risks of PCU. Some studies show increased risks when the family of origin is a one-parent-family, the mother has experienced problems with psychotropic substance or sexual assault or a dysfunction family situation is indicated by violence inside the family. Peers can be a risk especially when drugs are used regularly within this group or when they supply its members with the substances. In special settings like prisons or clubs the prevalence of PCU is much higher than in the normal population (Table 2).
Table 2: Antecedent factors of problem cannabis use
Area Specific aspect
Demographic factors Gender
Education
Psychotropic substances Alcohol
Mental disorders
Nicotine addiction
Conduct disorders
Early psychological disorders
Evidence for negative effects
+ male
+ low level
+ regular use before the age of 14
+ getting drunk for the first time
before the age of 14
+
+
+
Family situation
Social situation
Incomplete family situation
Drug use mother
Alcohol problems mother
Sexual assault
Experience of violence
Interrupted education
Drug using peers
Drug supply through friends
+
+
+
+
+
+
+
+
Special settings
(clubs, prisons) +
Conclusions from literature on factors/effects of the specific aspect: +: evidence found -: no evidence found
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5.2 Acute effects of problem cannabis use
Cannabis use produce a state of intoxication which changes perception and other parameter of somatic and mental state. It shows acute effects on heart rate and blood pressure, which may be problematic if a preceding damage exists. Cannabis smoke seem to be much more toxic and carcerogenic than tobacco smoke. Other acute consequences of cannabis use are only minor obstacles for well-being and health: dryness of the mouths, dizziness.
Acute effects on memory and cognitive functioning in general have been shown. This reduces psycho-motor abilities and interferes with the ability to drive a car or to operate complicated machines while intoxicated.
Panic attacks, anxiety and depressive moods can appear after cannabis use. Especially experiences of anxiety have been reported by a considerable percentage of users. More intense negative experiences are associated to acute toxic psychoses which are connected with a high dose and/or frequent use in most cases (Table 3).
Table 3: Overview acute effects of problem cannabis use
Area
Somatic
Mental
Specific aspect
Intoxication
Mortality
Cardio-vascular effects pulse beat increased blood pressure increased/
decreased
Respiratory system
Psycho-motor functioning
Others: dryness of mouth, cough
Cognition
Affect
Short term memory
Attention
Toxic effects
Toxic psychosis (“ cannabis psychosis”)
“Flashback”
Evidence for negative effects
+
-
+
+
+
+
+
+
-
+
+
Dysphoria
Anxiety
Panic attacks
+
+
+
Conclusions from literature on factors/effects of the specific aspect: +: evidence found -: no evidence found
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5.3 Chronic effects of problem cannabis use
There is an unsolved debate on the question, if effects caused through cannabis are stable and become chronic or if all of these impairments are temporary only. In many fields risks which have been discussed and suspected earlier or have been found in animal models have not been verified by human research or additional studies later.
In the field of somatic effects negative consequences of cannabis use on genetics, the immune system and reproduction have been discussed before, but these hypothesis have not been supported by research evidence so long. Also the risk of cancer of prostate and head or neck seems is increased through cannabis use. Critical are the effects of smoking cannabis for the respiratory tract. The risk of bronchitis is increased and there is also research indicating an increased risk of lung cancer through cannabis. The findings, that cannabis smoke is much more toxic than cigarette smoke are in line with this assessment.
Until now this risk has not produced a measurable increase in caseload of lung cancer in the population parallel to the increased cannabis use in many countries during the last 30 years.
This might be a result of a comparatively low frequency of use of cannabis for most of the users compared to tobacco. However, it can not be excluded that these consequences will become apparent in the population only with a delay of decades.
Chronic psychological effects have been found for cognition and memory. They last longer than the acute effect of cannabis do prevail but there is no study which shows persisting cognitive effects after an abstinence period of three weeks. Cannabis use can delay developmental processes and interfere with the personal development of an adolescent or young adult.
Cannabis use can cause harmful use and addiction as well as other problems linked to these syndromes: tolerance and withdrawal symptoms. High frequent, intensive use of cannabis means an increased risk of addiction; the duration of drug use does not play a crucial role in this respect. The degree of addiction seems to be lower than for a number of other drugs which makes detoxification easier and more successful.
A number of psychiatric problems have been discussed related to cannabis use. There is evidence that psychotic disorders and cannabis use correlate, but it is difficult to judge the type of association. A causal relationship is very hard to proof and – at the epidemiological level of evidence – an increase in incidence of schizophrenic disorders has not been found as a consequence of the increased cannabis use in the population of many countries of the
Western world. The use of cannabis as self-medication by schizophrenics tends to worsen the situation of the patient, active symptoms of psychotic disorders are increased. Anxiety disorders are rather frequent amongst cannabis users and increased risks of depression as a consequence of cannabis use has been shown especially for female users. “Amotivational syndrome” from cannabis use today is by most researchers seen as the effect on continous intoxication through cannabis. “Cannabis psychosis” are explained by short term effects of toxic psychosis, which can follow especially heavy use of cannabis. Long term psychotic effects caused by cannabis are subsumed under the general syndromes (Table 4).
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Table 4: Overview chronic effects of problem cannabis use
Area
Somatic
Specific field
Genetic harm
Immune system
Reproduction
Bronchitis
Cancer
Lung
Bronchi
Oesophagus
Head/neck
Prostate
Evidence for negative effects
-
-
-
+
+
+
+
-
-
Mental Perception
Cognition
Memory
Development
Dependence syndrome
Tolerance
+
+
+
-
+ up to 3 weeks after use
+
Withdrawal
Harmful use of other substances
Psychotic disorders
+
+
+
Anxiety Disorders
„Cannabis psychosis“
„Amotivational syndrome“
+
= toxic psychosis
= continued intoxication
Conclusions from literature on factors/effects of the specific aspect: +: evidence found -: no evidence found
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5.4 Secondary effects of problem cannabis use
Beside the effects of cannabis on somatic or mental health secondary effects have been shown in several fields. Given the critical age of many of the cannabis users, which are at the beginning of their adulthood trying to find a job and their place in life and society these secondary effects might in many instances be the most problematic ones.
There is clear evidence, that not only motivation but also ability to perform at the level of one´s possibilities is reduced through cannabis use. Reduced performance at school and workplace, lower marks at school and broken-off school or university education are associated with cannabis use. These effects are also a consequence of the cognitive impairments caused by cannabis described above. Even if these impairments do not persist after 3 weeks of abstinence, continuous intoxication through regular use of cannabis has the same negative effect on the performance.
The same impairments also lead to problems in driving a car, but most evidence shows only very limited negative effects in this respect. Cannabis users seem to counterbalance their impairment by driving more slow and more cautiously (Table 5).
Table 5: Overview secondary effects
Area
Unborn children
Performance and social adaptation
Specific field
Reduced birth weight
Cognitive impairment
Social adaptation
Problem in school and workplace
Reduced school and work performance
Traffic accidents
Evidence for negative effects
+
+ (only at the age of 4)
+
+
+
Traffic accidents
+ (small effect)
Crime Maladaptation
Violent acts
+
-
Conclusions from literature on factors/effects of the specific aspect: +: evidence found -: no evidence found
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6 Data analysis of national reports on treated problem cannabis users in Europe
The results from the national reports of the following member states were used as a basis for the following chapter. While the outline of this national chapter was defined by the EMCDDA guidelines some of the details differ between the national reports. For that reason data are not always completely comparable, but they can give an indication of the situation in different member states of the EU.
The analysis is based on the respective sub-chapters of the National REITOX reports for the year 2002 prepared by
Austria
Belgium
Czech Republic
Denmark
Finland
France
Germany
Greece
Ireland
Italy
Lithuania
Luxembourg
Netherlands
Netherlands
Norway
Portugal
Slovenia
Spain
Sweden
United Kingdom
In order to avoid duplication only the most interesting and relevant information has been drawn from the national reports and structured around the topics of prevalence, treatment demand, characteristics of clients, treatment needs and referrals, and special interventions for this group of clients offered in the reporting country. The full details can be found in the national REITOX reports prepared by the respective National Focal Points.
31
Prevalence
Problem cannabis use has been defined by the majority of countries through daily or nearly daily use of the substance. In some cases ICD-10 or DSM-IV clinical classifications were used. Most countries fall in the range of 0,2-3,0%. Less problematic patterns of use are more frequent. PCU is much more spread in special settings like prisons or youth help centres
(Table 6).
Table 6: Prevalence of problematic cannabis use (PCU) in Europe
Country Comments
Austria
Belgium
Czech Republic
Denmark regular use, age group 15+ use once per week, age group 12-25
Finland constant users suffering from physical, social, mental damage use during last 30 days
France
Germany
Greece
Ireland
(almost) daily use within last 2 weeks, age group 17-75
Cannabis dependence (DSM-IV), age group 14-24, lifetime prevalence dependence, age group 18-59, last year prevalence abuse, age group 14-24, lifetime prevalence used when alone problems through cannabis use (self-report)
17% cannabis abusers in clinical group with primary schizophrenic disorder
Italy
Lithuania
Luxembourg
Netherlands
Netherlands
Cannabis dependence (DSM-IIIR) age group 18-64 years, last years prevalence
Problem youth in Rotterdam, age 14-17, cannabis use during
11+/30 last days and having related problems
Norway
Portugal
Slovenia used cannabis more than 10 times in the last 6 months
Daily use among prison population
Used cannabis more than 40 times in lifetime, age-group_
15-16 (ESPAD), used cannabis during the last 12 months daily use during last 12 months Spain weekly use during the last 12 months
Sweden
United Kingdom cannabis dependence only, age group 16-74
Prevalence
4,6%
Male: 14,7%
Female: 7,1%
--
--
N=6.000
1%
N=40.000
3%
0,9%
0,2%
4%
9%
~ 1%
--
--
--
--
0,3-0,8%
20%
3%
6%
2%
2%
4%
--
3%
32
Treatment demand
Data on treatment demand are not really complete and some of the countries can describe the situation only through highly selective samples of treament facilities. From 19 (future) member states reporting, only two reported a reduction in prevalence over the last 10 years.
5 counties cannot give an indication on trends, but 13 member states reported an increasing trend (Table 7).
Table 7: Demand for treatment for PCU in Europe
Country Prevalence Type Trend over 10 years
Comments
Austria
Austria
20-25% use cannabis OR hallucinogens (2001) very rare
18 cases dependence, 45 cases of abuse (ICD9) (2002)
--
751 cases with main drug cannabis
(2002)
21% of treatment demands (2002)
18% of treatment demands (2002)
23% of treatment demands (2002)
27% of treatment demands (2002)
Out
In
?
national survey per treatment units almost always linked with mental disorders
City of Prague
Belgium
Czech
Republic
Denmark
Finland
France
Germany
Greece
Ireland
Italy
7% of treatment demands (2002)
15% of treatment demands (2000)
8% of treatment demands (2001)
All
All
-
?
?
All
Out
Out
All
All
Percentage or drug users treated decrease since 1999
Great regional variation, regional trend reported
Lithuania
Netherlands
Norway
Portugal
Slovenia
Spain
Sweden
United
Kingdom
6% of treatment demands (2000)
Luxembourg 11% of treatment demands (2002)
24% of treatment demands (2002)
Out
All
Out
?
Percentage of drug users treated
Percentage of drug users treated
9% (females), 16% (males) of treatment demands (2001)
All extremely small number (2003)
8% of treatment demands (2002)
7% of treatment demands (2001)
50% of clients below 20 years, 27% of clients above 20 years of age
All
All
All
All
?
expert opinion expert opinion
9% of treatment demands in England,
7% in Scotland use only cannabis
All
= increase, = decrease; = unchanged; ? = not available
33
Characteristics of problem cannabis users
Despite very different treatment settings all over Europe, clients share some common characteristics: 74-90% of the clients are male, in most countries the biggest age-group is 20 to 25 years. The big percentage of cannabis users still goes to school and lives with the parents. Problem cannabis users visit the treatment centre because of problems with family, school or work-place, addiction problems or other psychiatric disorders. By far the majority of cannabis users is well integrated into family, school or working-place (Table 8).
Table 8: Characteristics of PCU clients in treatment in Europe
Country Characteristics
Austria Gender: primary males
Socio-economic state: socially integrated
Problems: often psychotic disorders
-- Belgium
Czech Republic Gender: 74% male Age: 62% between 15 and 20 years,
Drug use: 51% use cannabis not more than 2 years
Problems: 39% parents; 30% discipline, 23% school
Denmark Gender: 81% male Age: males: 26 years, females: 28 years
Socio-economic state: 54% receive cash benefits, 10% daily benefits
Problems: handling daily activities, average marks and absence from school
Finland Gender. 79% male
Education: 70% primary level
Age: 20,2 years
Socio-economic state : 29% unemployed
Drug use: 40% 2 nd problem substance alcohol, duration of C. use: 5 years
Problems: depression, school attainment, psychoses
France
Germany
Greece
Ireland
Italy
Lithuania
Luxembourg
Netherlands
Gender: 82% male Age: 25,5 years
Drug use: 40% have a 2 nd problem substance, in most cases alcohol
Problems: social achievements (school, work)
Gender: 82% male Age: main age group 18-25 years
Drug use: 22% have alcohol as a 2 nd problem substance, 20% ecstasy
Problems: social achievements (school, work)
Gender: 88% male Age: mean 23 years
Socio-economic state : 81% live with their family, 33% unemployed
Problems: Psychiatric comorbidity
Gender: 85% male Age: Start of drug use at 15, begin treatment at 20
(outside Greater Dublin)
--
Problems: depression, mood disorders
Norway
Portugal
Problems: 33% had previous demands for psychiatric treatments
Gender: 80% male Age: 85% older than 20
Drug use: most have problems also with other substances, biggest increase for single users and users with cannabis plus alcohol problems
Problems: Increased 12 months prevalence of cannabis use for people with mood disorders (7,1%), mixed mood/anxiety disorders (8,8%) compared to people without such disorders (3,2%)
Problems: younger ones “dropping out” of family, school and social context, older clients show more often mental problems: anxiety/ depression/ general antisocial behaviour, Increased problems at school and workplace
Problems: Amotivational syndrome and psychoses are frequent
34
Table 8: Characteristics of PCU clients in treatment in Europe (continued)
Slovenia
Spain
Gender: 68% male Age: 19 years (first treatment demanders)
Drug use: 66% used cannabis daily for the last 6 months
Gender: 90% Age: begin use at 16, start treatment at 24 years
Drug use: 58% used alcohol during the last 30 days, 43% cocaine
Problems caused by cannabis: accidents 40%, missed class 41%, economic problems 33%, conflicts with family 30%, difficult at work 30%
Sweden
United Kingdom
Dysfunctional family background
Drug use: get drunk on a regular basis, 20% use additional drugs as well
Males: 75% Age: 30-40% below 20 years
Treatment needs and referrals
Between 19 and 44% or the clients come by themselves without the activities of any other person or institution. Where an comparison between the age-groups above and below 20 years was made, the percentage of self-referred clients is considerably higher in the older group of clients.
Parents, family and friends are important mediators and motivators when it comes to treatment. Between 26 and 90% of the clients have been referred by these persons when they come to drug treatment.
Referral through judicial proceedings or police interventions is of specific interest as there has been the hypotheses, that a growing pressure through law enforcement has created the increase in treatment demands for cannabis related problems. While law enforcement is an important actor, in most countries only 20-30% of all clients enter treatment this way. Only
Austria reports a much higher percentage for a subset of treatment facilities which are reporting to the national level. No country draw the conclusion from there national data, that changes in law or legal practice were sufficient to explain the increase in treatment demands found (Table 9).
35
Table 9: Treatment needs and referral for PCU clients in Europe
Country
Austria
Austria
Austria
Belgium
Czech Republic
Denmark
Finland
France
Germany
Greece
Ireland
Italy
Lithuania
Luxembourg
Netherlands
Norway
Portugal
Slovenia
Spain
Sweden
United Kingdom
Treatment needs and referral
Many do not need medical treatment or psychosocial care for cannabis use
¾ of clients referred to by authorities
Mixing users with opiate addicts and poly drug users very problematic
Information basis
Expert opinion
Assessment
Expert opinion
--
Referral: 40% self referred, 30% family Treatment statistics
Different from traditional treatment institutions and heroin addicts, additional problems besides drugs
Expert opinion
Referral: 19% self referred, 26% family/friends
Referral: 24% result of judicial proceedings
Referral: 25% of males, 20% of females comes as a result of judicial procedures or by order of public authorities
Referral: 19% self referred, 57% family/friends
Referral: 44% self referred/family /friends, 22% court/ probation/ police
--
Treatment statistics
Treatment statistics
Treatment statistics
Treatment statistics
Treatment statistics
Expert opinion Referral: majority through police (driving under influence of drugs), parents
Referral: Parents/school most frequent most problem cannabis users avoid the specialised drug treatment centre for unknown reasons referrals (<20 years): 35% self referred, 19% familiy/ friends, 9% Justice referrals (>=20 years): 42% self referred, 3% familiy/ friends, 14% Justice
--
--
--
-- gender: <20years: 60% male, >=20: 80% male referrals (<20 years): 90% family/ friends, 6% school, 4% social welfare referrals (>=20 years): 43% self referred, 18% family/ friends, 21% social welfare, 5% justice
Referral: 26-29% self referred, 4-9% family
/friends, 12-23% GPs/primary care teams/psychiatrist, 7-9% probation/police
Study
Treatment statistics
36
Specific treatment offers for problem cannabis users
In most cases for the treatment and care of problem cannabis users standard procedures and programmes are applied. In some cases, however, it has been criticised that mixing up cannabis clients with heroin users in treatment might not be the most efficient way to treat this group.
In addition to that a number of more specific approaches have been mentioned, which should be looked at and evaluated in more depth in future to develop more efficient methods of treatment for this specific clientele. Some elements can be grouped in the following way.
Short-term treatments
A very limited number of contact (up to about 5) are used for information, develop risk perception and risk competence, or should help to quit smoking cannabis
Integrative interventions
Elements of secondary prevention play an important role in some interventions which can be characterised by a intensive cooperation between different institutions (youth help, drug help, law enforcement)
Peer education
In a number of cases elements of peer education play an important role to better reach problem cannabis users but also to offer help and support to this group despite a lack of adequate public funding.
Beside these specific interventions the reports mention that treatment of cannabis related problems is also taking place within standard health care. The British report underlines, that
GPs as well as (tobacco) smoking cessation programmes do see and treat a considerable number of cannabis users.
37
Table 10: Special treatment offers for PCU in Europe
Country
Austria
Belgium
Czech Republic
Denmark
Finland
France
Germany
Greece
Ireland
Italy
Lithuania
Luxembourg
Netherlands
Norway
Portugal
Slovenia
Spain
Sweden
United Kingdom
Treatment provision
Short term counselling programme (max. 5 contacts)
Information and increased risk competence through peer education
--
Combined social services and interventions
Municipal dedicated peer teams for very young cannabis users
Acupuncture for cannabis users with depression disorder
No special institutions, but specific programmes. Multi partnership project outside the field of drug treatment
Peer education for driving licence groups
Counselling unit for adolescent drug users (KETHEA) integerating counselling, community intervention, social support and family support
--
--
--
MSF youth solidarity project: intervention team in collaboration with youth magistrate and law enforcement
Ongoing review of existing treatment programmes
Self-help internet programme
6weeks course: Smoking cessation for cannabis users to “free young people’s resources” under discussion
-- no specific interventions
Manual based cognitive behavioural therapy for cannabis users
Use of general health care: 25% of 20 GPs in Inner London researched in 2001 treated cannabis problems within the last 4 weeks smoking cessation programmes used: 24% of clients in a smoking cessation clinic hat used cannabis during the last 4 weeks
38
7 Recommendations for research and methodological developments for assessment at European level
Options for assessment
An increase in prevalence of cannabis use has been found in most EU member states during the last years (EMCDDA 2003). The trend for problem cannabis use (PCU) is not totally clear due to a lack of common standards of data collection and reporting. There are several ways to assess problem cannabis use:
Assessing PCU through high frequent of use
For this purpose items can be used which are already included in the EMCDDA model questionnaire for population surveys. A cut-off value for the frequency of cannabis use for the last 12 months should be set for PCU, which would make comparisons between countries easier.
Assessing PCU through qualitative aspects of use: dependence/ harmful use/ abuse
The criteria for harmful use or dependence correlate with frequency of use, but target negative consequences instead of patterns of use. For both aspects EMCDDA standards have not been defined yet, but existing instruments could be used. The
CIDI has been used in a number of international studies as an instrument for personal interviews and its items also have been applied successfully in selfadministered questionnaires.
Possible sources of information
The relevant information could be drawn from a number of data sources:
Surveys
The items should be integrated in surveys or administered separately in a standardised way in the population or in treated groups.
Treatment demand statistics
A qualified description of persons with PCU can be produced with little effort by treatment facilities based on the concept of main drug (TDI). As only a minority of persons with PCU are seen by specialised treatment facilities, this indicator can deliver information on trends and characteristics of PCU but not on the prevalence.
Research studies
A more reliable way to produce diagnoses is based on personal interviews. While in this way a high data quality can be reached for example through the application of
CIDI, costs and efforts are rather high as well. This solution seems reasonable for research purposes but not adequate for monitoring purposes.
39
Proposals for methodological development
From a number of possible actions two are proposed, which seem especially important and cost-effective:
1. The TDI at the moment offers some helpful information on treated cannabis clients.
While the standards have been widely accepted and are applied in most countries, in some areas there is still only a limited level of standardisation given. The definition of
“primary drug” in treatment until now can be implemented in the Member States in different ways and in fact only a small number of country explicitly follows the international standards ICD-10 or DSM-IV. This is a possible risk for comparability with not empirical evidence to judge its size. A recent German study has shown reasonable good quality of diagnosis for primary cannabis related cases (Simon &
Sonntag, in print), but as the German system is based since 10 years on ICD-10 standards this does not answer the question for other countries.
Therefore diagnostic procedures should be defined more precise in addition to the
TDI standards taking into account the diagnostic criteria of ICD/DSM in order to produce prevalence data on the basis of international diagnostic standards. This should take place at least for subsets of treated clients in every member state. A small research study in a representative sample of countries should check on the basis of a limited number of clients (N=50 per country) intercorrelation between classification as usual and classification on the basis of a more rigorous definition following ICD/DSM.
2. Existing screening instruments should be further developed to come up with a simple but sensible instrument, which can classify cannabis users on the basis of drug use patterns in two or three groups according to the degree of risk or problems bound to their drug use. This instrument could at the same time serve as a screening instrument in drug treatment in order to find the most applicable intervention for each cannabis users asking for help and collect epidemiological data within surveys and treatment monitoring.
In order to increase cost-effectiveness it should be discussed if such an action could take into account also other substances like amphetamines, ecstasy and cocaine, which also play a big role in recreational use of drugs on one side and can be cause of problems and treatment needs on the other side.
40
8 Bibliography
8.1 Assessment
American Psychiatric Association American Psychiatric Association (APA) (1994). Diagnostic and
Statistical Manual of Mental Disorders , 4 th ed .
. Washington: American Psychiatric Association.
Adamson, S. J., Sellman, J. D. (2003). A prototype screening instrument for cannabis use disorders: the Cannabis Use Disorders Identification Test (CUDIT) in an alcohol-dependent clinical sample. Drug Alcohol Rev, 22 , 309-315.
Benson, G., Holmberg, M. (1985). Validity of questionnaires in population studies on drug use. Acta
Psychiatrica Scandinavica , 71 , 9-18.
Buchan, B.J., Dennis, M.L., Tims, F.M., Diamond, G.S. (2002). Cannabis use: consistency and validy of self-report, on-site urine testing and laboratory testing. Addiction, 97 , (Suppl. 1), 98-108.
Chalsma, AL, Boyum W. (1994). Marijuana situation assessment. September 1994. Office of National
Drug Control Policy, Washington.
Cummins, L.H., Chan, K.K., Burns, K.M., Blume, A.W., Larimer, M., Marlatt, G.A. (2003). Validity of the CRAFFT in American-Indian and Alaska-Native adolescents:screening for drug and alcohol risk. J Stud Alcohol, 64 , (5), 727-32.
Dilling, H., Mombour, W. & Schmidt, M.H. (Hrsg.) (1999). Internationale Klassifikation psychischer
Störungen: ICD-10, Kapitel V (F). Klinisch-diagnostische Leitlinien. 3. Auflage. Göttingen:
Huber.
Gmel, G. (1998). Konsistenz des selbstberichteten Lebenszeitkonsums von Cannabis in der Schweiz:
Ergebnisse einer Studie über acht Jahre. Abhängigkeiten, 4 , 15-21.
Gossop, M., Darke, Sh., Griffiths, Pö. Hando, J., Powis, B., Hall, W., Strang., J. (1995). The severity of dependence scale (SDS): psychometric properties of the SDS in English and Australian samples of heroin, cocaine and amphetamine users. Addiction, 90 , 607-614.
Knight, J.R., Sherritt, L., Shrier, L.A., Harris, S.K., Chang, G. (2002). Validity of the CRAFFT substance abuse screening test among adolescent clinic patients. Arch Pediatr Adolesc Med,
156 , (6), 607-14.
Kokkevi, A. & Hartgers, H. (1995).EuropASI.: European adaptation of a multidimensional assessment instrument for drug and alcohol dependence. Eur Addict Res 1995;1: 208-10.
Kraus, L. Augustin, R. (2001). Measuring alcohol consumption and alcohol-related problems: comparison of responses from self-administered questionnaires and telephone interviews.
Addiction, 96 , 459-471.
Lahey, B.B., Flagg, E.W., Bird, H.R., Schwab-Stone, M.E., Canino, G., Dulcan, M.K., Leaf, P.J.,
Davies, M., Brogan, D., Bourdon, K., Horwitz, S.M., Rubio-Stipec, M., Freeman, D.H.,
Lichtman, J.H., Shaffer, D., Goodman, S.H., Narrow, W., Weissman, M.M., Kandel, D.B.,
Jensen, P.S., Richters, J.E., Regier, D.A. (1996). The NIMH Methods for the Epidemiology of
Child and Adolescent Mental Disorders (MECA) Study: background and methodology. J Am
Acad Child Adolesc Psychiatry, 35 , (7), 855-64.
McLellan, A.T., Luborsky, L., Cacciola, J., Griffith, J., McGahan, P., O'Brien, C.P. (1985). Guide to the addiction severity index: background, administration, and field testing results. Rockville MD:
National Institute on Drug Abuse.
Meyer, C., Rumpf, H-J., Hapke, U., John, U. (o.J.). The Composite International Diagnostic Interview: feasibility and necessity of editing and interviewer training in general population surveys.
International Journal of Methods in Psychiatric Research, 9 , 32-42.
Miller, N.S., Gold, M.S. (1989). The diagnosis of marijuana (cannabis) dependence. J Subst Abuse
Treat, 6 , 183-192.
Regier, D.A., Farmer, M.E., Rae, D.S., Locke, B.Z., Keith, S.J., Judd, L.L., Goodwin, F.K. (1990).
Comorbidity of mental disorders with alcohol and other drug abuse. Results from the
Epidemiologic Catchment Area (ECA) Study. JAMA, 264 , (19), 2511-8.
Regier, D.A., Kaelber, C.T., Rae, D.S., Farmer, M.E., Knauper, B., Kessler, R.C., Norquist, G.S.
(1998). Limitations of diagnostic criteria and assessment instruments for mental disorders.
Implications for research and policy. Arch Gen Psychiatry, 55 , (2), 109-15.
41
Reynaud, M., Schwan, R., (2003). Diagnosis of drug addiction , Rev Prat, 53 , (12),1304-14.
Robins, L.N., Wing, J., Wittchen, H.-U., Helzer, J.E., Barbor, T.F., Burke, J., Farmer, A., Jablensky, A.,
Pickens, R., Gerier, D.A., Sartorius, N., Towle, L.H.. The Composite International Diagnostic
Interview: An epidemiological instrument suitable for use in conjunction with different diagnostic systems and in different cultures. Archives of General Psychiatry, 1988 , 1069-77.
Saunders, J. B., Aasland, O.G., Babor, T.F., de la Fuente, J. R. , Grant, M., (1993). Development of the Alcohol Use Disorders Identification Test (AUDIT): WHO Collaborative Project on Early
Detection of Persons with Harmful Alcohol Consumption – II, Addiction. 88 , 791-804.
Schwab-Stone, M., Regier, D., Canino, G. (1999). Features of interviews questions associated with attenuation of symptom reports. J Abnorm Child Psychol, 27 , (6), 429-37.
Shaffer, D., Fisher, P., Dulcan, M.K., Davies, M., Piacentini, J., Schwab-Stone, M.E., Lahey, B.B.,
Bourdon, K., Jensen, P.S., Bird, H.R., Canino, G., Regier, D.A.. (1996). The NIMH Diagnostic
Interview Schedule for Children Version 2.3 (DISC-2.3). J Am Acad Child Adolesc Psychiatry,
35 , (7), 865-77.
Ustun, B., Compton, W., Mager, D., Babor, T., Baiyewu, O., Chatterji, S., Cottler, L., Gogus, A.,
Mavreas, V., Peters, L., Pull, C., Saunders, J., Smeets, R., Stipec, M.R., Vrasti, R., Hasin, D.,
Room, R., Van den Brink, W., Regier, D., Blaine, J., Grant, B.F., Sartorius, N. (1997). WHO
Study on the reliability and validity of the alcohol and drug use disorder instruments: overview of methods and results. Drug Alcohol Depend, 47 ,(3), 161-9.
Wittchen, H.-U. & Pfister, H. (eds.)(1997).DIA-XInterviews: Manual für Screening-Verfahren und
Interview. Swets & Zeitlinger, Frankfurt.
Wittchen, H.-U., Robins, L.N., Cottler, L.B., Sartorius, N., Burke, J.D., Regier, D. (1991): Cross-cultural feasibility, reliability and sources of variance of the Composite International Diagnostic
Interview (CIDI). The Multicentre WHO/ADAMHA Field Trials. Br J Psychiatry, 159 , 645-58.
World Health Organisation (WHO) (1992) . International Statistical Classification of Diseases and
Related Health Problems, Tenth Revision. World Health Organization, Geneve.
8.2 Substance
Bundeskriminalamt (BKA) (2003). Rauschgiftjahresbericht 2002, BKA, Wiesbaden.
Coffey, C., Lynskey, M., Wolfe, R., Patton, G.C.(2000).Initiation and progression of cannabis use in a population-based Australian adolescent longitudinal study. Addiction, 95 , (11), 1679-90.
ElSohly, M.A., Ross, S.A., Mehmedic, Z., Arafat, R., Yi, B., Banahan, B.F. (2000). Potency trends of delta9-THC and other cannabinoids in confiscated marijuana from 1980-1997. Journal of
Forensic Sciences, 45 , 24-30.
European Opinion Research Group (EORG) (2002). Attitudes and opinions of young people in the
European Union on drugs. Eurobarometer 57.2, Special Eurobarometer 172. Indra (Europe),
Brussels.
Hall, W., Degenhardt, L., Lynskey, M. (2001). The health and psychological effects of cannabis use.
Monograph Series, 44 . Commonwealth of Australia, Canberra.
Hoch, E., Simon, R., Hüllinghorst, R., Nöcker, G., Spahlinger, M. P. (2002). Bericht zur
Drogensituation. Deutsche Referenzstelle für die Europäischen Beobachtungsstelle für
Drogen und Drogensucht (DBDD), Munich.
Johansson, E., Ohlsson, A., Lindgren, J.E., Agurell, S., Gillespie, H., Hollister, L.E. (1987).Single-dose kinetics of deuterium-labelled cannabinol in man after intravenous administration and moking.
Biomed Environ Mass Spectrom, 14 , (9), 495-9.
Kaa, E., Bowmann, H. (1998). [The illicit drug market in Aarhus I.Supply].Ugeskr Laeger., 160 , 5035-7.
Korf, D.J. (2002), Dutch coffee shops and trends in cannabis use. Addictive Behaviors, 27 , (6), 851-
866.
Korf, D.J., Nabben, T., & Benschop, A. (2002). Antenne 2001 : trends in alcohol, tabak, drugs en gokken bij jonge Amsterdammers. Rozenberg Publishers, Amsterdam.
Mahhadian, E., Newcomb, M.D., & Bentler, P.M. (1986). Adolescents' substance use: impact of ethnicity, income, and availability. Adv Alcohol Subst Abuse. 5, 63-78.
Matthias, P., Tashkin, D.P., Marques-Magallanes, J.A., Wilkins, J.N., Simmons, M.S. (1997). Effects of varying marijuana potency on deposition of tar and delta9-THC in the lung during smoking.
Pharmacol Biochem Behav , 58 , (4), 1145-50.
42
Mikuriya, T.H., Aldrich, M.R., (1988). Cannabis 1988. Old drug, new dangers. The potency question. J
Psychoactive Drugs, 20 , (1):47-55.
Mura, P., Perrin, M., Chabrillat, M., Chaudron, H., Dumestre-Toulet, V., Barc, S. et al. (2001),
L'augmentation des teneurs en delta9 tétrahydrocannabinol dans les produits à base de cannabis en France : mythe ou réalité ? Annales de Toxicologie Analytique, 13 , (2), 75-79.
Smart, R.G., Adlaf, E.(1989). Student cannabis use and enforcement activity in Canada: 1977-1987.
Drug Alcohol Depend, 24 , (1), 67-74.
Simon, R., Sonntag, D. (in press). Cannabisbezogene Störungen: Umfang, Behandlungsbedarf und
Behandlungsangebot in Deutschland. Bonn: BMGS.
Simon, R., Spegel, H., Hüllinghorst, R., Nöcker, G., David-Spickermann, M. (2002). Bericht des
Nationalen REITOX Knotenpunkts für Deutschland an die EBDD: Drogensituation 2001.
DBDD, München.
Wachtel, S.R., ElSohly, M.A., Ross, S.A., Ambre, J., deWit, H. (2002). Comparison of the subjective effects of delta(9)-tetrahydrocannabinol and marijuana in humans. Psychopharmacology
(Berl), 161 , 331-119.
8.3 Problem use
Adams, I., Martin, B.R. (1996). Cannabis: pharmacology and toxicology in animals and humans.
Addiction, 91 , 1585-1614.
Agar, M. (1995). Concept Abuse in the Drug Field. The International Journal of the Addictions, 30 , (9),
1165-1168.
Allebeck, P., Adamsson, C., Engström, A. (1993). Cannabis and Schizophrenia: a longitudinal study of cases treated in Stockholm County. Acta Psychiatrica Scandinavica, 88 , 21-24.
Andreasson, S., Allebeck, P. (1990). Cannabis and mortality among young men: A longitudinal study of Swedish conscripts. Scandinavian Journal of Social Medicine, 18 , 9-15.
Andréasson, S., Allebeck, P., Engström, A., Rydberg, U. (1987). Cannabis And Schizophrenia – A
Longitudinal Study of Swedish Conscripts. The Lancet, 26 , (December 1987), 1483-1485.
Andréasson, S., Allebeck, P., Rydberg, U. (1989). Schizophrenia in users and nonusers of cannabis – a longitudinal study in Stockholm County. Acta Psychiatrica Scand, 79 , 505-510.
Arseneault, L, Cannon, M., Poulton, R., Murray, R., Caspi, A., Moffitt, T.E. (2002). Cannabis use in adolescence and risk for adult psychosis : Longitudinal prospective study. BMJ, 325 , 1212-
1213.
Atha, M.J., Davis, S. (2003). The Government’s drug policy: follow-up. Submission of Independent
Drug Monitoring Unit to House of Commons Home Affairs Select Committee, 6th March 2003 .
Babor, T.F., Webb, C., Burleson, J.A., Kaminer, Y. (2002). Subtypes for classifying adolescents with marijuana use disorders: construct validity and clinical implications.
Beck, F., Legleye, S., Peterri-Watel, P. (2002). Penser les drogues: perceptions des produits et des politiques publiques. Enquête sur les représentations, opinions et perceptions sur les psychotropes (EROPP) 2002.
Bell, R., Wechsler, H., Johnston L.D. (1997). Correlates of college student marijuana use: results of a
US National Survey. Addiction, 92 , (5), 571-581.
Berke, J., Hernton, C. (1974). The Cannabis Experience. An interpretative study of the effects of marijuana and hashish. London: Peter Owen.
Bijl, R.V., Ravelli, A. (1998). Psychiatrische morbiditeit, zorggebruik en zorgbehoefte. Resultaten van de Netherlands Mental Health Survey and Incidence Study (Nemesis). Tijdschrift voor
Gezondheidswetenschappen, 76 , 446-457.
Bland, R., Newman, S., Orn, H. (1987). Schizophrenia: Lifetime co-morbidity in community sample.
Acta Psychiatrica Scandinavica, 75 , 383-391.
Bovasso, G.B. (2001). Cannabis abuse as a risk factor for depressive symptoms. American Journal of
Psychiatry, 158 , 2033-2037.
Bowman, M., Pihl, R.O. (1973). Cannabis: psychological effects of chronic heavy use: a controlled study of intellectual functioning in chronic users of high potency cannabis. Pharmacologia, 29 ,
159-170.
43
Boys, A., Farrell, M., Taylor, C., Marsden, J., Goodman, R., Brugha, T., Bebbington, P., Jenkings, R.,
Boys, A., Farrell, M., Taylor, C., Marsden, J., Goodman, R., Brugha, T., Bebbington, P.,
Jenkings, R., Meltzer, H. (2003). Psychiatric morbidity and substance use in young people aged 13-15 years: results from the Child and Adolescent Survey of Mental Health. Br. J.
Psychiatry, 182 , 509 - 517.
Brook, J.S., Balka, E.B., Whiteman, M. (1999). The risks for late adolescence of early adolescent marijuana use. American Journal of Public Health, 89 , 1549-1554.
Budney, A.J., Moore, B.A., Vandrey, R.G., Hughes, J.R. (2003). The time course and significance of cannabis withdrawal. Journal of Abnormal Pychology, 112 , 393-402.
Caspari, D. (1998). Cannabismissbrauch bei Schizophrenen – Ein Vergleich mit Patienten ohne
Suchtproblematik. Sucht, 44 , 162-168.
Cleghorn, J., Kaplan, R., Szechtman, B., Szechtman, H., Brown, G., Franco, S. (1991). Substance abuse and schizophrenia: Effect on symptons but not on neurocognitive Function. Journal of
Clinic Psychiatry, 52 , 26-30.
Coffey, C., Lynskey, M., Wolfe, R., Patton, G.C.(2000).Initiation and progression of cannabis use in a population-based Australian adolescent longitudinal study. Addiction, 95 , (11), 1679-90.
Coggans, N., Dalgarno, P., Johnson, L. and Shewan, D. (2002). Long-term heavy cannabis use.
Research report submitted to the Department of Health. University of Strathclyde.
Corr, C. (1999). Health and homelessness: Health status and health care access of single homeless men living in hostels in inner city Dublin. Unpublished thesis – Submitted as part of Degree in
Master of Science in Applied Social Research, University of Dublin, Trinity College, Dublin.
Dennis, M., Babor, T.F., Roebuck, M.C., Donaldson, J. (2002). Changing the focus: the case for recognising and treating cannabis use disorders. Addiction, 97 , (Suppl. 1), 4-15.
Der, G., Gupta, S., Murray, R.M. (1990). Is schizophrenia disappearing?. Lancet, 1 , 513-516.
Dixon, L., Haas, G., Weiden, P., Sweeney, J., Frances, A. (1990). Acute Effects of Drug Abuse in
Schizophrenic Patients: Clinical Observations and Patient´s Self-Reports. Schizophrenia
Bulletin, 16 , 70-79.
Duwe, A., Schu mann, J., Küfner, H. (2001). Deviantes Verhalten und späterer Drogenkonsum. suchtmed, 3 , 73-82.
Eidgenössische Kommission für Drogenfragen (1999). Cannabisbericht. Bern: Bundesamt für
Gesundheit.
Eikmeiner, G., Lodemann, E., Pieper, L, Gastpar, M. (1991) Cannabiskonsum und Verlauf schizophrener Psychosen [Cannabis Use and the Course of Schizophrenia]. Sucht, 6 , 377-
382.
Engelsmann, E.L. (1989). Dutch Policy on the Management of Drug-related Problems. British Journal of Addiction, 84 , 211-218.
European Monitoring Centre for Drugs and Drug Addiction (2000b). Complementary statistical tables to the Annual Report on the state of the drugs problem in the European Union [Online]. http://www.emcdda.org/publications_annrepstat_00.smhtl [2000, October 11].
European Opinion Research Group (EORG) (2002). Attitudes and opinions of young people in the
European Union on drugs. Eurobarometer 57.2, Special Eurobarometer 172 . Indra (Europe),
Brussels.
Fahrenkrug, H., Müller, R., Müller, S. (2001). Cannabis in der Schweiz: Eine Droge auf der Schwelle zum legalen Rauschmittel. Abhängigkeiten, 1 , 5-32.
Farrell, A.D., Danisch, S.J., Howard, C.,W. (1992). Relationship between drug use and other problem behaviours in urban adolescents. Journal of Consulting and Clinical Psychology, 60 , 705-712.
Fergusson, D. & Horwood, J. (1997) Early onset cannabis use and psychosocial adjustment in young adults. Addiction, 92 , 279-296.
Fergusson, D.M., Horwood, L. J. (2001). Cannabis use and traffic accidents in a birth cohort of young adults. Accid Anal Prev, 33 , 703-11.
Fergusson, D.M., Horwood, L.J., Beautrais. A.L. (2003).Cannabis and educational achievement.
Addiction, 98, 1681-1692.
Fischer, U. C. , Jung, C., Müller, S., Kuntsche, E.N. (2001). Die psychischen Wirkungen von Cannabis
– Ein Überblick über den aktuellen Forschungsstand. abhängigkeiten, 3 , 30-47.
Fletcher, J.M., Page, J.B., Francis, D.J., Copeland, K., Naus, M.J. et al. (1996). Cognitive correlates of long-term cannabis use in Costa Rican men. Arch Gen Psychiatry, 53 , 1051-1057.
44
Fried, P. A. (1993). Prenatal exposure to tobacco and marijuana: Effects during pregnancy, infancy, and early childhood. Clinical Obstetrics and Gynecology, 36 , (2), 319-337.
Fried, P., Watkinson, D.J., Gray, R. (2002). Current and former marijuana use: preliminary findings of a longitudinal study of effects on IQ in young adults. CMAJ, 166 , 887-891.
Geschwinde, T. (2003). Rauschdrogen. Spinger-Verlag, Berlin.
Grant, I., Gonzalez, R., Carey, C.L., Natarajan, L., Wolfson, T. (2003). Non-acute (residual) neurocognitive effects of cannabis use: A meta-analytic study. Journal of the International
Neuropsychological Society, 9 , 679-689.
Green, B.E, Riffer, C. (2000). Marijuana use and depression. Journal of Health and Social Behavior,
41 , 40-49,2000.
Hackauf, H., Winzen, G. (1999). On the state of young people’s health in the EU.
Haney, M., Ward, A.S., Comer, S.D., Foltin, R.W, Fischman, M.W. (1999). Abstinence symptoms following smoked marijuana in humans. Psychopharmacology, 141 , 395-404.
Häfner, H., Bühler, B., Hambrecht, M., Löffler, W., Maurer, K., & an der Heiden, W. (2002). .
Vorzeitige Auslösung der Schizophrenie durch Substanzmissbrauch und Folgen für den weiteren Verlauf". Nervenheilkunde, 4 .
Hall, W., Degenhardt, L., Lynskey, M. (2001). The health and psychological effects of cannabis use.
Monograph Series, 44 . Commonwealth of Australia, Canberra.
Hall W, Degenhardt L. (2000). Cannabis and psychosis (Australia/Newzealand), 34 , 26-34.
Hall, W., Room, R. (1995). A comparative appraisal of the health and psychological consequences of alcohol, cannabis, nicotine and opiate use. Background paper prepared for the WHO project
„Cannabis: a health perspective and research agenda". Meeting on health implications of cannabis use, Geneva, 22-24 May 1995 .
Hall, W., Solowij, N. (1997). Long-term cannabis use and mental health. British Journal of Psychiatry,
171 , 107-108.
Hall, W., Solowij, N. (1998). Adverse effects of Cannabis. Lancet, 352 , 1611-1616.
Hall, W., Solowij, N., Lemon, J. (1994). The health and psychological consequences of cannabis use.
National Drug Strategy, Monograph Series no 25 , Australian Government Publishing
Service, Canberra.
Hambrecht, M., Häfner, H. (1996). Führen Alkohol- oder Drogenmissbrauch zu Schizophrenie?, 67 ,
36-45.
Hell, D. (1970). Der Gebrauch von Cannabis unter Jugendlichen Zürichs. Zeitschrift für
Präventivmedizin, 15 , 331-157.
Höfler, M., Lieb, R., Perkonigg, A., Schuster, P., Sonntag, H. & Wittchen, H-U. (1999). Covariates of cannabis use progression in a representative population sample of adolescents: a prospective examination of vulnerability and risk factors. Addiction, 94 , 1679-1694.
Hollister, L.E. (1986). Health Aspects of cannabis. Pharmacological Reviews, 38 , 2-20.
Hollister, L.E. (1998). Health Aspects of Cannabis: revisited. International Journal of
Neuropsychopharmacology, 1 , 71-80.
Hopkins, N.. Community backs cannabis pilot scheme. Guardian Unlimited, 22.3.2002
.
Hurrelmann, K., Bründel, H. (1997). Drogengebrauch, Drogenmissbrauch. Eine Gratwanderung zwischen Genuß und Abhängigkeit. Wissenschaftliche Buchgesellschaft, Darmstadt.
Inserm (2001). Cannabis. Quels effets sur le comprtement et la santé ? Les éditions Inserm, Paris.
Iversen, L.L. (2000). The science of Marijuana. Oxford University Press, New York.
Jääskeläinen J. (2003). Cannabis predispose depression and anxiety [Available only in Finnish]
Duodecim 2003, 119 , 195.
Jessor, R., Jessor, S. L. (1977). Problem behaviour and psychosocial development: A longitudinal study of youth. Academic Press, San Diego.
Johnson, B. (1990). Psychopharmacological effects of cannabis. British Journal of Hospital Medicine,
43 , 114-122.
Johnson, B., Smith, B., Taylor, P. (1988). Cannabis and Schizophrenia. The Lancet, 1988 , 592-93.
Kammer-Spohn, M. (2001). Cannabiskonsum bei Patienten im allgemeinpsychiatrischen
Behandlungsbereich. Abhängigkeiten, 3 , 68-70.
45
Kandel, D.B., Davies, M. (1996). High School Students Who Use Crack and Other Things. Archives of
General Psychiatry, 52 , 71-80.
Kandel, D.B., Johnson, J.G., Bird, H.R., Weissman, M.M., Goodman, S.H., Lahey, B.B., Regier, D.A.,
Schwab-Stone, M.E.(1999). Psychiatric comorbidity among adolescents with substance use disorders: findings from the MECA Study. J Am Acad Child Adolesc Psychiatry, 38 , (6), 693-9.
Kay, R. (1992). Prevalence and incidence of schizophrenia in Afro-Caribbeans. British Journal of
Psychiatry, 421 .
Kessler, R.C., Aguilar-Gaxiola, S., Andrade, L., Borges, G., Caraveo-Anduaga, J.J., DeWit, D.J.,
Kolody, B., Merikangas, K.R., Molnar, B.E., Vega, W.A., Walters, E.E., Wittchen, H.-U., Ustun
T.B. (2001). Mental-substance comorbidities in the ICPE surveys (English). Psychiatrica fennica, 32, (2), 62-79.
Kilpatrick, D.G., Acierno, R., Saunders, B., Resnick, H.S., Best, C.,L., Schnurr, P.P. (2000). Risk factors for adolescent substance abuse and dependence. Data from a national sample.
Journal of consulting and clinical psychology, 68 , 19-30.
Kleiber, D. & Kovar, K.-A. (1997). Auswirkungen des Cannabiskonsums. Wissenschaftliche
Verlagsgesellschaft, Stuttgart.
Kleiber, D., Soellner, R. (1998). Cannabiskonsum in der Bundesrepublik Deutschland:
Entwicklungstendenzen, Konsummuster und Einflussfaktoren. Juventa, Weinheim.
Kleiber, D., Stosberg, K., Täschner, K.-L., Tossmann, H.P., Wiesbeck, G.A. (1992).
Erfahrungen mit Cannabiskonsumenten. Ergebnisse einer Umfrage bei Kliniken und
Drogenberatungsstellen. Sucht, 38 , 7-17.
Kraus, L. & Augustin R. (2001). Repräsentativerhebung zum Gebrauch psychoaktiver Substanzen bei
Erwachsenen in Deutschland 2000. [Population Survey on the Consumption of Psychoactive
Substances in the German Adult Population 2000]. IFT Institut für Therapieforschung,
München.
Krüger, H.-P., Schulz, E., Magerl, H. (1998). Medikamenten- und Drogennachweis bei verkehrsunauffälligen Fahrern. Roadside Survey. Berichte der Bundesanstalt für das
Straßenwesen, Heft M60. Wirtschaftsverlag NW, Bremerhaven.
Küfner, H., Duwe, A., Schumann, J., Bühringer, G. (2000). Prädiktion des Drogenkonsums und der
Suchtentwicklung durch Faktoren in der Kindheit: Grundlagen und Ergebnisse einer empirischen Studie. Sucht, 46 , 32-53.
Lagier, G., Le Chuiton, J., Dally, S., Facy, F., Got, C., Lafargue, P. et al. (1996). Livre blanc : sécurité routière, drogues licites ou illicites et médicaments : rapport au premier minister. La
Documenta tion française, Paris.
Lieb, R., Isensee, B., von Sydow, K., Wittchen, H-U. (2000). The Early Development Stages of
Psychopathology Study (EDSP): A Methodological Update. European Addiction Research, 6 ,
170-182.
Lieb, R., Schuster, P., Pfister, H., Fuetsch , M., Höfler, M., Isensee, B., Müller, N., Sonntag, H.,
Wittchen, HU. (2000). Epidemologie des Konsums, Missbrauchs und der Abhängigkeit von legalen und illegalen Drogen bei Jugendlichen und jungen Erwachsenen: Die prospektivlongitudinale Verlaufsstudie EDSP. Sucht, 46 , 18-31.
Liniger, B. (2001). Die Bedeutung des Hanfs in der Verkehrsmedizin – Auswirkungen des
Cannabiskonsums auf Fahrfähigkeit und Fahreignung. abhängigkeiten, 3 , 71-74.
Lucas, C.P., Fisher, P., Piacentini, J., Zhang, H., Jensen, P.S., Shaffer, D., Dulcan, M., Maddahian, E.,
Newcomb, M.D., Bentler, P.M. (1986). Adolescents' substance use: impact of ethnicity, income, and availability. Adv Alcohol Subst Abuse, 5 , (3), 63-78.
Lynskey, M.T., Heath, A.C. , Kathleen K. Bucholz, K. K., Wendy S. Slutske, W. S., Madden,P. A. F.
Nelson, E. C., Statham, D. J., Martin, N. G. (2003). Escalation of drug use in early-onset cannabis users vs co-twin controls. JAMA, 289 , 427-433.
Linszen, D.H., Dingemans, P.M., Lenior, M.E. (1994). Cannabis abuse and the course of recent-onset schizophrenic Disorders. Archives of General Psychiatry, 51 , 273-279.
McGee, R., Williams, S., Poulton, R., Moffitt, T. (2000). A longitudinal study of cannabis use and mental health from adolescence to early adulthood. Addiction, 95 , 491-503.
Meyer, C., Rumpf, H-J., Hapke, U., Dilling, H., John, U. (2000). Lebenszeitprävalenz psychischer
Störungen in der erwachsenen Allgemeinbevölkerung . Ergebnisse der TACOS Studie.
Nervenarzt, 71 , 535-542.
46
Meyer, C., Rumpf, H-J., Hapke, U., John, U. (o.J.). The Composite International Diagnostic Interview: feasibility and necessity of editing and interviewer training in general population surveys.
International Journal of Methods in Psychiatric Research, 9 .
Miller, D., Miller, T. (1997). A test of socioeconomic status as a predictior of initial marijuana use.
Addictive Behaviors, 22 , 479-489.
Miller P., Plant M. Heavy cannabis use among UK teenagers: an exploration. Drug Alcohol Depend
2002, 65 , 235-242.
Ministry of Public Health in Belgium (2002). Cannabis 2002 Report. A joint international effort at the initiative of the Ministers of Public Health of Belgium, France, Germany, The Netherlands,
Switzerland. Technical Report of the International Scientific Conference. Brussels, Belgium,
25/2/2002 . Ministry of Public Health in Belgium, Brussels.
Müller R., Meyer M., Gmel G. (1997). Alkohol, Tabak und illegale Drogen in der Schweiz 1994-1996.
Mura, P. (1999). Alcool, médicaments, stupéfiants et conduite automobile. Elsevier, Paris.
Narring g. Tschumper A. Michaud P-A (1994). Die Gesundheit Jugendlicher in der Schweiz. Institut universitaire de medicine sociale et preventive, Lausanne.
Narrow, W.E., Rae, D.S., Robins, L.N., Regier, D.A.(2002). Revised prevalence estimates of mental disorders in the United States: using a clinical significance criterion to reconcile 2 surveys' estimates. Arch Gen Psychiatry, 59 , (2), 115-23.
Negrete, J. (1988). What´s Happened to the Cannabis Debate? British Journal of Addiction, 83 , 359-
372.
Negrete, J. (1989). Cannabis and Schizophrenia. British Journal of Addiction, 84 , 349-351.
Norton, R., Colliver, J. (1988). Prevalence and patterens of combined alcohol and marijuana use.
Journal of Studies on Alcohol, 49 , (4), 378-380.
Norton, R., Colliver, J. (1988). Prevalence and Patterns of Combined Alcohol and Marijuana Use.
Journal of Studies on Alcohol, 49 , 378-380.
Ouwehand, A.W, Cruts, A.A.N. (1997). Problematisch Cannabisgebruik nader beschouwd. IVV,
Houten.
Page, J.B., Fletcher, J.M., True, W.R. (1988). Psychosocial perspectives on chronic cannabis use :
The Costa Rican follow-up. Journal of Psychoactive Drugs, 20 , 57-65.
Patton, G.C., Coffey, C., Carlin, J.B., Degenhardt, L, Lynskey, M., Hall, W. (2002). Cannabis use and mental health in young people: cohort study. BMJ, 325 ,1195-1198.
Pencer, A., Addington, J. (2003). Substance use and cognition in early psychosis. Rev. Psychiatry
Neurosci, 28 , 48-54.
Peralta, V., Cuesta, M. (1992). Influence of cannabis abuse on schizophrenic psychopathology. Acta
Psychiatrica Scandinavica, 85 , 127-130.
Perkonigg, A. Beloch, E., Garzynski, E., Nelson, C., Pfister, H., Wittchen, HU. (1997). Prävalenz von
Drogenmissbrauch und –abhängigkeit bei Jugendlichen und jungen Erwachsenen: Gebrauch,
Diagnosen und Auftreten erster Missbrauchs- und Abhängigkeitsmerkmale. Zeitschrift für
Klinische Psychologie, 26 , 247-257,
Perkonigg, A., Lieb, R., Höfler, M., Schuster, P., Sonntag, H. & Wittchen, H-U. (1999). Patterns of cannabis use, abuse and dependence over time: incidence, progression and stability in a sample of 1228 adolescents. Addiction, 94 , 1663-1678.
Perkonigg, A., Lieb, R., Wittchen, H-U. (1998). Substance Use, Abuse and Dependence in Germany –
A review of Selected Epidemiological Data. European Addiciton Research, 4 , 8-17.
Pedersen, W. (1998). BitterSott. Universitetsforlaget, Oslo.
Phillips, L.J. , Curry, C., Yung, A.R., Yuen, H.P., Adlard, S., Mc Gorry P.D. (2002). Cannabis is not associated with the development of psychosis in an ‘ultra’ high-risk group. Austr NZJ
Psychiatry, 36 , 800-806.
Pir kola S. (2003): Kannabis ja skitsofrenia. [Cannabis and schizophrenia] Pääkirjoitus. Duodecim
2003, 119 , 1119-1200.
Poel, A. van der, Mheen, D. van de (1999). Softdrugs in Midden-Holland. Een onderzoek naar de omvang en achtergronden van softdrugsgebruik. IVO/GGD Midden-Holland, Rotterdam /
Gouda.
Poikolainen K.(2002). Kannabis lisää masennuksen vaaraa.[Cannabis increases the risk of depression] Duodecim 2002, 118 , 421.
47
Polen, M.R., Sidney, S., Tekawa, I., Sadler, M., Friedmann, G.D. (1993). Health Care Use by Frequent
Marijuana Smokers Who Do Not Smoke Tobacco. The Western Journal of Medicine, 596-601.
Pope, H.G., Gruber, A. J., Hudson, J.I., Huestis, M. A., Yurgelun-Todd, D. (2001). Neuropsychological performance in long-term cannabis users. Archives of General Psychiatry, 58 , 909-915.
Pope, H.G., Ionescu-Pioggia, M., Aizley, H.G., Varma, D.K. (1990). Drug Use and Life Style Among
College Undergraduates in 1989: A Comparison With 1969 and 1978. American Journal of
Psychiatry, 147 , 998-1001.
Quensel, S. (2000). Medikamente brauchen, Cannabis, Rauchen: Die Rolle des Pharmakonsum bei
14jährigen Schülerinnen und Schülern in Bremen. Wiener Zeitschrift für Suchtforschung, 23 ,
(2 ) , 33-44.
Regier, D.A., Farmer, M.E., Rae, D.S., Locke, B.Z., Keith, S.J., Judd, L.L., Goodwin, F.K. (1990).
Comorbidity of mental disorders with alcohol and other drug abuse. Results from the
Epidemiologic Catchment Area (ECA) Study. JAMA, 264 , (19), 2511-8.
Regier, D.A., Narrow, W.E., Rae, D.S., Manderscheid, R.W., Locke, B.Z., Goodwin, F.K..(1993). The de facto US mental and addictive disorders service system. Epidemiologic catchment area prospective 1-year prevalence rates of disorders and services. Arch Gen Psychiatry, 50 , (2),
85-94.
Reusser, F. (2001). Joint-Adventure oder Tablette? Zur Kultur des Hanfgebrauchs mit seiner Tradition und heutigen Praxis in der Schweiz. abhängigkeiten, 3 , 5-10.
Rey, J.M., Sawyer, M.G., Raphael, B., Patton, G.C., Lynskey, M.T. (2002). The mental health of teenagers who use marijuana. Br J Psychiatry, 180 , 222-226.
Righter H., van Laar, M. (2002). In Ministry of Public Health in Belgium: Cannabis 2002 Report.
Ministry of Public Health in Belgium, Brussels.
Robins, L.N. (1977). Detecting predictors of rare events – Demographic, family, and personal deviance as predictors of stages in the progression toward narcotic addiction [In: H.M. Babigian
(Hrsg.).The Origins and Course of Psychopathology]. Plenum Press, New York.
Rohr, M.J., Skowlund, S.W., Martin, T.E. (1989). Withdrawal Sequelae to Cannabis Use. The
International Journal of the Addictions, 24 , 627-631.
Russell, J.M., Newman, S.C., Bland, R.C. (1994). Drug Abuse and Dependence. Acta Psychiatrica
Scandinavia, Suppl. 376, 54-62.
Sabroe, S. & Fonager, K. (2002). Rusmiddelforbruget – i folkeskolens afgangsklasse og udviklingen fra 1995-99 . Udgivelse nr. 40. FADL’s Forlag, København.
Satz, R., Fletcher, J.M., Sutker, L.S. (1976). Neuropsychologic, intellectual, and personality correlates of chronic marijuana use in native Costa Ricans. Ann N Y Acad Med, 822 , 266-306.
Schneier, F., Siris, S. (1987). A Review of Psychoactive Substance Use and Abuse in Schizophrenia.
The Journal of Nervous and Mental Disease, 175 , 641-652.
Schulz E., Vollrath, M., Klimesch, C.l, Szegedi, A. (1998). Fahruntüchtigkeit durch Cannabis,
Amphetamine und Cocain. Literaturanalyse. Berichte der Bundesanstalt für Straßenwesen.
Wirtschaftsverlag NW, Bremerhaven.
Schumann, J., Augustin, R., Duwe, A. & Küfner, H. (2000). Welchen Einfluss haben erste Erfahrungen und Begleitumstände zu Beginn des Drogenkonsums auf den weiteren Verlauf? Zeitschrift für
Gesundheitspsychologie, 8 , 69-82.
Sexton, B.F., Tunbridge, R.J. Brook-Carter, N., Jackson, P.G., Wright, K., Stark, M.M. et al. (2000).
The influence of cannabis on driving. Transport Research Laboratory.
Shedler, J., Block, J. (1990). Adolescent Drug Use and Psychological Health, 1990. American
Psychologist, 612-630.
Sidney, S., Beck J.E., Tekawa, I.S., Quesenberry, C.P., Friedman, G.D. (1997). Marijuana Use and
Mortality. American Journal of Public Health, 87 , (4), 585-590.
Simon, R., Spegel, H., Hüllinghorst, R., Nöcker, G., David-Spickermann, M. (2002). Bericht des
Nationalen REITOX Knotenpunkts für Deutschland an die EBDD: Drogensituation 2001.
DBDD, München.
Smit, F., Bolier, L., & Cuijpers, P. (in press). Cannabisgebruik en de kans op latere schizofrenie: een bespreking van de recente literatuur. Nederlands Tijdschrift voor Geneeskunde.
Soellner, R., Kleiber, D. , Tossmann, H.P. (1995). Einmal Cannabis - immer Cannabis?
Prädiktoren für fortgesetzten Cannabiskonsum. Verhaltenstherapie und psychosoziale Praxis,
65-77.
48
Strang, J., Witton, J., Hall, W. (2000). Improving the quality of the cannabis debate: defining the different domains. BMJ, 320 , 108-110.
Substance Abuse and Mental Health Services Administration, Office of Applied Studies. Emergency
Department Trends form the Drug Abuse Warning Network, Preliminary Estimates January –
June 2002. DAWN Series, D-22 . DHHS Publication, Rockville.
Tennent, F., Groesbeck, J. (1972). Psychiatric Effects of Hashish. Archives of General Psychiatry, 27 ,
133-136.
Tashkin, D. P. (1991). Marihuana and the Lung.[In: Nahas, G.G. et al. (Eds.). Marihuana and
Medicine]. Humana Press, Totowa.
Thomas, H. (1993). Psychiatric symptoms in cannabis users. British Journal of Psychiatry, 163 , 141-
149.
Thomas, H. (1996). A community survey of adverse effects of cannabis use. Drug and Alcohol
Dependence, 42 , 201-207.
Thornicroft, G. (1990) Cannabis and Psychosis – Is there Epidemiological Evidence for an
Association?. British Journal of Psychiatry, 157 , 25-33.
Tims, F.M., Dennis, M.L., Hamilton, N., Buchan, B.J., Diamond, G., Funk, R., Brantley, L.B. (2002).
Characteristics and problems of 600 adolescent cannabis abusers in outpatient treatment.
Addiction, 97 , (Suppl. 1), 46-57.
Torres, A. & Gomes, M. C. (2002), Drogas e prisões em Portugal. IPDT, Lisbon.
Troisi, A., Pasini, A., Sracco, M., Spalletta, G. (1998). Psychiatric symptoms in male cannabis users not using other illicit drugs. Addiction, 93 , 487-492.
Van der Poel, A. & Van de Mheen, D. (1999). Softdrugs in Midden-Holland : een onderzoek naar de omvang en achtergronden van softdrugsgebruik. IVO, Rotterdam. van Laar, M., Cruts, A. Rigter, H., Verdurmen, J. , Meijer, R., van Ooyen, J. (2003). National Drug
Monitor. 2002 Annul Report. Trimbos, Utrecht. van Os, J., Bak, M., Hanssen, M., Bijl, R. V. R., de Graaf, R., Verdoux, H. Cannabis Use and
Psychosis: A Longitudinal Population-based Study. Am J Epidemiol 2002, 156 , 319-327. von Sydow, Lieb, R., Pfister, H., Höfler, M., Sonntag, H. & Wittchen, H-U. (2001). The natural course of cannabis use, abuse and dependence over four years: a longitudinal community study of adolescents and young adults. Drug and Alcohol Dependence, 64 , (3 ) , 347-361.
Williams, J.H., Wellman, N.A., Rawlins, J.N.P. (1996). Cannabis use correlates with schizotypy in healthy people. Addiction, 91 , 869-877.
Wittchen, H-U., Lieb, R. & Perkonigg, A. (1999). Early Development Stages of Substance Abuse and
Dependence – Examples from a Prospective Longitudinal Study, in Ladewig, D. (ed): Basic and Clinical Science of Substance Related Disorders. Bibl. Psychiatr., 168 , 7-22. Karger,
Basel.
Wittchen, H-U., Perkonigg, A., Lachner, G., Nelson, C. (1998). Early Development Stages of
Psychopathology Study (EDSP): Objectives and Design. European Addiction Research, 4 , 18-
27.
Woody, G.E., Cottler, L.B., Cacciola, J. (1993). Severity of dependence: data from the DSM-IV field trials. Addiction, 88 , 1573-1579.
Wu, T-C., Tashkin, D.P., Djahed, B., Rose, J.E. (1988). Pulmonary Hazards of Smoking Marijuana as compared with Tobacco. The New England Journal of Medicine, 316 , 347-351.
Zammit, S., Allebeck, P., Andreasson, S., Lundberg. I.. Lewis, G. Self reported cannabis use as a risk factor for schizophrenia in Swedish conscripts of 1969: historical cohort study. BMJ 2002; 325-
1199.
49
