From:
Crano, W.D., and Burgoon, M. (Eds.) Q0a4. Mass Media and Drug prevention:
Classic and contemporary theories and researc&. . New Jersey: Lawrence Erlbaum
Associates, Publishers
10
High-potential Mediators of
Drug-Abuse Prevention Program Effects
Stewart l. Donaldson
Cl are
mont
G rad u
ate
U n ive
rsitY
Drug prevention efforts designed by social scientists do not work.
Despite billions of dollars invested in prevention, America's drug problem
is alive and well. Face it, we have lost the war on drugs.
Supply reduction approaches (law enforcement) are effective, but
demand reduction (prevention) is hopeless.
The most popular drug-abuse prevention program in America today is
not effective, and represents the largest waste of taxpayer resources in
the history of prevention and health education.
These statements and perspectives are part of the popular discourse
about drug-abuse prevention at the turn of the century. These and similar
claims are commonly voiced in the mass media, by human service professionals working with youth on a day-to-day basis, in policy arenas, and
in the drug-abuse prevention research literature. Given these views and
your current thoughts about the effectiveness of drug-abuse prevention,
please take a moment and answer the following forced-choice questions:
1. Do drug-abuse prevention interventions work?
a. Yes
b.
No
2. Do drug-abuse prevention interventions work?
a. Always
b. Sometimes
c.
d.
Rarely
Never
215
216
DONALDSON
lf you answered No to question 1, or c or d to question 2, you agree with
the majority of people I have asked to answer these queitions. ln fact,
despite numerous talks and discussions about the promise of drug prevention at this conference, the majority of the audience was still skeptical
about the effectiveness of social-science-based drug prevention efforts
when I asked these questions during my late afternoon talk. lf drugabuse prevention programs are not effective, why do we continue to
spend billions of dollars annually on them? why is there a large federal
research and demonstration project budget for drug-abuse prevention?
And, why is there a burgeoning literature on the topic? The answer is that
asking the common question of whether or not drug prevention programs
work is much too simplistic for this complex topic. one purpose of this
chapter is to convince you that whether or not an intervention works is the
wrong question to ask in the drug-abuse prevention area.
TYPES OF INTERVENTION RESEARCH
Knowledge about drug-abuse prevention is generally based on three
types of research: preintervention research, efficacy research, and effectiveness research (see Donaldson, 19g9; Foxhall, 2000). preinteruention
research typically focuses on theory testing and basic relationships
between drug use and various psychological factors. This research is
most often conducted before time and resources are invested in program
development. systematic knowledge about the correlates of drug use
can be very informative for designing drug-abuse prevention programs.
Efficacy research sets out to study an actual intervention under
somewhat controlled conditions. That is, a researcher designs the intervention often using social science theory and preintervention research as
a guide, and then implements the program as strongly as possible. The
idea is to make sure the program is delivered at futt-strength in a constrained setting and on a limited sample of clients, to determine if it affects
drug use. The same researcher or research team usually designs and
conducts the evaluation of the intervention in efficacy research. A major
advantage of this type of intervention research is that the research team
can maintain control of the evaluation and thus can control for extraneous
variables and sort out the causal effects of the program. Disadvantages
of efficacy intervention research include (a) the potLntial conflict of interest involved with evaluating a program one has designed, and (b) the
possibility that what can be achieved under ideal conditions cannot
be
replicated under real world conditions (e.g., when delivered in a school, a
community, or via mass media).
1
O. HIGH-POTENTIAL MEDIATORS
217
ln contrast, effectiveness research investigates the effects of a program delivered in a "real-world" setting. That is, once a program is taken
to scale and implemented with the intention of solving specific problems
(as opposed to mainly aiding research interests and goals), the effectiveness of the intervention is evaluated. ln an ideal program design sce-
of preintervention
research findings and tested under ideal conditions in an efficacy trial. lf
nario, an intervention is developed on the basis
the results are favorable, the intervention is implemented in society and
evaluated using effectiveness research procedures, including cost-effectiveness and cosVbenefits analyses (Donaldson, 2000; Rossi, Freeman,
& Lipsey, 1999). lnterventions that demonstrate positive results across all
three types of intervention research are believed to have the best chance
of solving social problems such as drug-abuse, and are good candidates
for future funding by local, state, and federal agencies.
It is possible that interventions judged effective by effectiveness
research have not been tested in efficacy research nor based on preintervention research. The drawback of betting heavily on this "streamlined"
approach is that many threats to validity often cannot be ruled out when
using effectiveness research alone. For example, randomized trials are
often beyond the scope of what is possible in effectiveness research; this
makes ruling out threats to internal validity quite challenging. Standardization and strict control over research procedures and design are often
difficult obtain, and this can introduce undesirable error variance into
results. ln contrast, an intervention that has shown positive results in preintervention and efficacy research but not in effectiveness research is
also risky because it is often very difficult to replicate effects found in controlled studies out in society (external validity issues). The benefit of relying on all three types of intervention research (vs. just one or two) is that
the strengths and weaknesses of each approach are typically offsetting.
Most threats to validity can be evaluated and hopefully ruled out across
the different types of studies.
One notable strength of effectiveness research is that it is more likely
to be designed in a way that protects against internal evaluation biases
(Scriven, 1991). There is a relativelywidely held belief in the evaluation
research community that internal evaluations, those evaluations done by
evaluators with some stake in positive findings (e.g., evaluators whose
financial compensation is in some way affected by intervention success,
evaluators who designed the intervention, evaluators who developed the
theory upon which the intervention is based, and the like), are less trustworthy than interventions subjected to rigorous external evaluation. ln the
ideal situation, external evaluators have a large stake in conducting a rigorous and objective evaluation that holds up under the scrutiny of meta-
DONALDSON
evaluation, serves the best interest of the consumer or intervention recipient, and the evaluators have no stake in whether or not the program is a
smashing success or a dismal failure. This is sometimes achieved in
effectiveness research by employing different teams to design, imple-
ment, and evaluate.
lt is
important to note that this could also be
achieved in efficacy research, but history suggests it is much less likely.
EXTERNAL EVALUATION PERSPEGTIVE
As might be expected, external evaluators, theory developers, intervention designers, and those who serve dual roles such evaluators and intervention designers often see the world very differenfly. For obvious
reasons, generally speaking, external evaluators are typically less enthusiastic about the potential of new interventions based on their view of the
past track record of intervention research. For example, the field of intervention research has been characterized by a history of disappointing
results and has been described as a "parade of close lo zero Effects"
(see Rossiet al., 1999;Shadish, Cook, & Leviton, 1991). Rossi(1985), in
a somewhat "tongue in cheek" presentation, introduced the five metallic
and plastic laws of program evaluation:
't'
2.
The lron Law: The expected value of any net impact assessment of
any social program is zero.
The stainless sfee/ Law: The better designed the impact assessment
of a social program, the more likely is the net impact to be zero.
3. The Copper Law: The more social programs are designed to change
individuals, the more likely the net impact will be zero.
4. The Plastic Law: only those programs that are likely to fail are evaluated.
5. The Plutonium Law'. Program operators will explode when exposed to
typical evaluation research findings.
Although humorous on the surface, these laws capture the essence of
how many external evaluators feel about the track record of social science-based programming. ln short, the history of external evaluation has
led many to believe that the American establishment of policymakers,
agency officials, professionals, and social scientists has not been effective at designing and implementing interventions to solve social problems
such as drug-abuse.
A recent example of this view in the drug-abuse prevention literature
involves evaluations of Project D.A.R.E., the most popular drug-abuse
10. HIGH.POTENTIAL MEDIATORS
219
prevention program in the United States. ln short, Project D.A.R.E. has
received record levels of government funding and has reached more than
4.5 million American children, despite a wealth of scientific evidence suggesting that it is not effective at preventing drug-abuse (Dukes, Ullman, &
Stein, 1996; Ennett, Tobler, Ringwalt, & Flewelling, 1994) and may even
be harmful under some conditions (Donaldson, Graham, Piccinin,
&
Hansen, 1995).Other.external evaluators have come to a very different
conclusion about the problem of null effects throughout the history of evaluation research. I have previously referred to this as the design sensdrvity problem prevalent in evaluation practice today (Donaldson, 1999). ln
short, this view suggests the dismal track record produced by external
evaluations of social science-based interventions is at least partly due to
the quality of the evaluations, not just the effectiveness of the interventions.
Lipsey (1988) presented one of the strongest arguments for the
design sensitivity position. Based on an extensive, systematic review of
the program evaluation literature, Lipsey argued that conventional evaluation research:
t.
z.
4.
5.
ls based on constructs that substantially underrepresent the complexity of the causal processes at issue.
ls theoretically impoverished and yields little knowledge of practical
value.
ls crudely operationalized and rarely meets even minimum standards
for quality design and measurement.
ls largely insensitive to the very treatment effects it purports to study.
Produces results and conclusions that are largely a matter of chance
and have little to do with the efficacy of the treatments under consideration.
Furthermore, Lipsey and Wilson (1993) subsequently meta-analyzed 111
meta-analyses of intervention studies across a wide range of program
domains (representing evaluations of more than 10,000 programs) and
reported that most of this literature was based on only crude outcome
research with little attention paid to potential mediating and moderating
factors.
Although most external evaluators have not been impressed with the
evaluation results of social-science-based interventions, there is not general agreement as to why this phenomenon has occurred. However,
regardless of whether it is the programs, the evaluations, or both that
have failed us in the past, many external evaluators now seem to agree
about the agenda for the next generation of intervention evaluations.
220
DONALDSON
simply stated, the question of interest should no longer be whether programs work but rather how they work and how they can be made to work
better (Donaldson,2000; Lipsey & Wilson, 1993, Rossi et al., 1999;
weiss, 1998). This approach should focus on the investigation of which
program components are most effective, the mediating causal processes
through which they work, and the characteristics of the participants, service providers, settings, and the like that moderate the relationships
between an intervention and its outcomes.
H
IGH.POTENTIAL MEDIATORS
Traditional program conceptualization and evaluation (as described earlier) focused on determining the direct effects of undifferentiated "black
box" interventions and on answering the question of whether or not inter-
ventions worked (see Figure 10.1). Again, a main drawback of this
approach is that very little is typically learned when no effect is found.
The evaluation researcher is not able to disentangle the success or failure
of implementation from the validity of the conceptual model or program
theory on which the intervention is based (Crano & Brewer, in press).
There is also no way to sort out which intervention components are effective, ineffective, or counterproductive. Furthermore, Hansen and McNeal
(1996) argued that behavioral interventions such as drug-abuse prevention programs can only have indirect effects. They called this the Law of
lndirect Effect:
This law dictates that direct effects of a program on behavior are not possible. The expression or suppression of a behavior is controlled by neural
and situational processes over which the interventionist has no direct
control. To achieve their effects, programs must alter processes that
have the potential to indirecfly influence the behavior of interest. simply
stated, programs do not aftempt to change behavior direcfly. lnstead
they attempt to change the way people think about the behavior, the way
they perceive the social environment that influences the behavior, the
skills they bring to bear on situation that augment risk for the occurrence
of the behavior, or the structure of the environment in which the behavior
will eventually emerge or be suppressed. The essence of health education is changing predisposing and enabling factors that lead to behavior,
not the behavior itself. (Hansen & McNeal, 1996, p. 503)
1
O. HIGH-POTENTIAL MEDIATORS
221
FIGURE 10.'t A direct effect model.
The new agenda for evaluation begins by recognizing that interventions
like drugabuse prevention programs are often complex and multidimensional, and aspire for indirect effects on drug use behavior.
ln its simple form, an indirect effect conceptualization involves an
intervention (e.g., drug prevention video program) affecting a mediator
variable (e.g., drug-abuse knowledge), which in turn affects an outcome
(e.g., drug use; see Figure 10.2). ln this example, the intervention must
be effective at increasing knowledge, and increased knowledge must lead
to reduced drug use for the intervention to be viewed as effective. There-
fore, the link between an intervention and a behavioral outcome is highly
dependent on the nature of the mediator/behavioral outcome relationship.
Hansen and McNeal (1996) called this the Law of Maximum Expected
Potential Effect:
The magnitude of change in a behavioral outcome that a program can
produce is directly limited by the strength of relationships that exist
between mediators and targeted behaviors. The existence of this law is
based on the mathematical formulae used in estimating the strength of
mediating variable relationships, not from empirical observation,
although we believe that empirical observations will generally corroborate its existence. An understanding of this law should allow intervention
researchers a mathematical grounding in the selection of mediating processes for intervention. An added benefit may ultimately be the ability to
predict with some accuracy the a priori maximum potential of programs
to have an effect on targeted behavioral outcomes, although this may be
beyond the current state-of-the-science to achieve. (Hansen & McNeal,
1996, p.502)
Therefore, within the specific context of an intervention, if the mediator variable can be adequately affected by the intervention, and the mediator has an adequately strong causal effect on the behavioral outcome, I
refer to this variable as a high-potential mediator. That is, a high-potential
DONALDSON
Prevention
Video
FIGURE 10.2
Knowledge
No Drug
Use
An indirect effect model.
mediator is a variable that has a strong probability of being affected by an
intervention, and subsequently affecting a behavioral outcome at a
desired level (i.e., has a practically significant effect size; see Donaldson,
Street, Sussman, & Tobler, 2000). Based on the preceding discussion,
now argue that a major challenge for the field of drug-abuse prevention is
making sure interventions are aimed at the right targets, high-potential
I
mediators.
ADOLESCENT DRUG.ABUSE PREVENTION
The field of drug-abuse prevention is vast and consists of many different
prevention approaches (e.9., primary, secondary, and tertiary prevention),
types of interventions (e.9., school, work site, community, and mass
media), target populations (e.9., children, adolescents, and young adults),
and behavioral outcomes (e.9., marijuana use, cocaine use, binge drinking, etc.). The pursuit of high-potential mediators must begin by specifying the particulars of the prevention intervention context. obviously, high-
potential mediators in one prevention context may be worthless in
another. To illustrate how one goes about identifying high-potential mediators of drug-abuse prevention interventions, I focus the subsequent discussion on one of the popular and challenging drug prevention problems,
the primary prevention of the onset of adolescent substance use.
A recommended first step in the process of selecting high-potential
mediators is to isolate the behavioral outcomes of interest. The "gateway
drugs" of cigarettes, alcohol, and marijuana use are often the main focus
of primary prevention interventions targeted at adolescents. lt is very
important to have realistic expectations for how a prevention intervention
may influence these behavioral outcomes. For example, it is not uncom-
1
O. HIGH-POTENTIAL MEDIATORS
mon to think that the goal of a drug-abuse prevention intervention is to
prevent adolescents from ever using or abusing drugs. This would be
ideal but is well beyond what can be realistically expected from most primary prevention efforts. A more realistic expectation for a primary pre-
to delay the onset of drug use and/or the
prevalence of use among at least a subgroup of a target population. lt is
important to underscore the point that many drug-abuse prevention interventions are ultimately judged as failures because initialbehavioralobjecvention intervention is
tives are unrealistic. lnterventions that deter the onset of substance use
are believed to be important because they prevent school failure and
other problem behaviors during the formative years of adolescents, and
the earlier adolescents begin using drugs, the more likely they are to
abuse drugs as young adults (Hawkins et al., 1997).
Once realistic behavioral outcomes are selected, theory and prior
research can be a good starting point for isolating high-potential mediator
variables that are likely to be strongly related to the behavioral outcomes
of interest. For example, Petraitis, Flay, and Miller (1995) reviewed 14
multivariate theories of experimental substance use among adolescents
and proposed a framework that organizes their central constructs into
three types of influence (social, attitudinal, and intrapersonal) and three
distinct levels of influence (proximal, distal, and ultimate). Each theoretical approach described suggests specific mediators, which vary in effectiveness across the various time frames (e.9., proximal versus distal
behavioral outcomes).
Even more specific to this illustration, Hawkins, Catalano, and Miller
(1992) conducted a thorough review of the literature and isolated 17 risk
and protective factors for the onset of drug use (see Table 10.1). lnterventions designed to prevent these risk factors are presumed to lower
rates of adolescent drug-abuse. However, it is clear to see from this table
that some risk/protective factors are much more likely to be influenced by
primary prevention interventions (e.9., attitudes, peer associations, family
practices) than others (e.9., neighborhood disorganization, some physiological factors). lt is important to underscore that high-potential mediators
must be both strongly causally related to the behavioral outcome of interest, and amenable to practically significant change by the intervention of
interest. Therefore, in a given prevention context, one must make sure
both that the set of targeted medrators are powerful enough to affect the
behavioral outcomes and that it is feasible to change them in the target
population.
There now is a large body of literature describing efforts to prevent
adolescent substance use. Hansen (1992, 1993) summarized lhe 12
most popular substance-abuse prevention strategies and identified their
224
DONALDSON
Table 10.1
Seventeen Risk and Protective Factors
for the Onset of Drug Abuse
Factor
't
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
#
Factor
Laws and norms
Availability
Extreme economic deprivation
Neighborhood disorganization
Physiologicalfactors
Family drug use
Family management practices
Family conflict
Low bonding to family
Early and persistent problem behaviors
Academic failure
Low commitment to school
Peer rejection in elementary grades
Association with drug-using peers
Alienation and rebelliousness
Attitudes favorable to drug use
Early onset of druq use
Note. Abstracted from Catalano and Miller (1992).
presumed theoretical program or mediating mechanisms (see Table
10.2). Although all three of these frameworks (Hansen, 1992, 1993;
Hawkins et al., 1992; Petraitis et al., 1995) and others (Newcomb & Earlywine, 1996; Wills, Pierce, & Evans, 1996) can be very useful for narrowing down the range of possibilities, it often is difficult to find evidence that
reveals which combination of mediators will produce the largest effects on
the behaviors of interest.
Fortunately, relatively recent mediation analyses in this area have
begun to isolate some of the strongest mechanisms at work in adolescent
drug-abuse prevention. This work has suggested that social-influencebased prevention programming is one of the most effective approaches
for preventing drug-abuse among young adolescents from general populations (see Donaldson et al., 1996). For example, MacKinnon et al.
(1991) found that social norms, especially among friends, and beliefs
about the positive consequences of drug use appeared to be important
mediators of program effects in project STAR (Students Taught Aware-
1
O. HIGH.POTENTIAL MEDIATORS
225
TABLE 10.2
Twelve Popular Substance-Abuse Prevention Strategies
Item
1
2
3
4
5
6
7
B
9
10
11
12
Normative education: Ddecreases perceptions about
prevalence and acceptability beliefs; establishes
conservative norms.
Refusal assertion training: lncreases the perception
that one can deal effectively with pressure to use
drugs if offered; increases self-efficacy.
lnformation about consequences of use: lncreases
perceptions of personal vulnerability to common
consequences of drugs.
Personal commitment pledges: lncreases personal
commitment and intentions not to use drugs
Values: lncreases perception that drug use is
incongruent with lifestyle
Alternatives: lncreases awareness of enjoying
life without drugs.
Goal-setting skills: lncreases ability to set and
achieve goals; increases achievement orientation
Decision-making skills: lncreases ability to make
reasoned decisions.
Self-esteem: lncreases feeling of self-worth.
Stress skills: lncreases perceptions of coping skills;
reduces reported level of stress.
Assistance skills: lncreases availability of help
Life skills: lncreases ability to maintain positive social
relations
Note: Adapted from Hansen (1992, 1993).
ness and Resistance). The program did not appear to have effects
through resistance skills (refusal training). The notion that social norms
are a potent aspect of prevention programming was subsequently found
in a randomized prevention trial, the Adolescent Alcohol Prevention Trial
(Donaldson, Graham, & Hansen, 1994; Donaldson et al., 1995).Continuing with the example, we might decide that a set of high-potential mediators, broadly conceived as social norms variables, are what we will try
to influence with a mass media drug-abuse prevention strategy. A careful
examination of how these variables are currently operating in the target
population is needed to determine what types of communication and data
226
DONALDSON
Moderator
Mediator
FIGURE 10.3
Outcome
A moderator effect model.
are most appropriate. lt is important to note that it is possible that for
some prevention problems, the variables most likely to affect the behavioral outcomes are not likely to be affected by the available prevention
strategy options. However, in this example, mass media prevention
approaches seem particularly well suited for influencing the social norm
variables identified in the adolescent drug-abuse prevention literature
(e.9., Donohew, Sypher, & Bukoski, 1991).
Once a set of high-potential mediators has been selected, it is important to consider potential moderators of the links in a mediation model of
drug-abuse prevention (see Donaldson, 2000). A moderator is a qualitative (e.9., gender, ethnicity, viewing setting) or quantitative (e.g., amount
of viewing prevention message, length of prevention message) variable
that affects the direction and/or strength of the relationships between the
intervention and mediator, or the mediator and the outcome (see Baron &
Kenny, 1986). Figure 10.3 illustrates that the moderator variable conditions or influences the path between the intervention and the mediator.
This means that the strength and/or the direction of the relationship
between the intervention and the mediator is significanfly affected by the
moderator variable. This type of moderator relationship is of primary
importance in drug-abuse prevention programming. lntervention designers can benefit greatly from considering whether or not potential modera-
10. HIGH-POTENTIAL MEDIATORS
tor variables such as participant characteristics, message characteristics,
characteristics of the viewing setting, and the like influence the intervention's ability to affect target mediators.
A series of evaluations is sometimes needed to fully understand
mediating and moderating effects of drug-abuse prevention interventions.
This is because many drug-abuse prevention interventions are complex,
context dependent, and delivered to target populations with diverse characteristics. A summary of findings from social-influence-based prevention
mediation studies mentioned previously provides a nice illustration of this
complexity. Following is a summary of key findings from evaluations of
the Adolescent Alcohol Prevention Trial:
1.
A
school culture change program (normative education) lowered
beliefs about drug use acceptability and prevalence estimates (in seventh grade), which predicted cigarette, marijuana, and cigarette use (in
eighth grade). This pattern of results was virtually the same across
potential moderators of gender, ethnicity, context (public vs. private
school), drugs and levels of risk and was durable across time (see
Hansen & Graham, 1991; Donaldson et al, 1994).
Resistance skills training did improve refusal skills, but refusal skills
did not predict subsequent drug use (Donaldson et al., 1994).
Those who received only resistance skills in public schools actually
had higher prevalence estimates (a harmful effect; type of school is
shown as the moderator; Donaldson et al., 1995).
Refusal skills did predict lower alcohol use for those students who had
negative intentions to drink alcohol (negative intention to drink is the
moderator; Donaldson et al., 1995).
The effects of normative education were subsequently verified using
reciprocal best friend reports of drug use, in addition to traditional self-
report drug use measures (Donaldson, Thomas, Graham, Au,
&
Hansen, 2000.
SUMMARY AND GONGLUSIONS
There remains considerable skepticism about our ability to use social science knowledge to prevent or solve social problems such as drug-abuse.
Although there often are promising early findings from preintervention
research and efficacy studies, the history of external evaluations of effectiveness research has been rather disappointing. Whether one interprets
the prevalence of null effects as the result of ineffective interventions or
insensitive external evaluations, most agree that modern evaluation
DONALDSON
research needs to move beyond just asking whether or not interventions
high-potential mediators promises to help us
understand how interventions work and how to design them to work bet-
work. A new focus on
ter.
The field of drug-abuse prevention seems ahead of the curve in identifying high-potential mediators of intervention effects. ln this chapter, I
summarized some of the recent literature on the primary prevention of
adolescent drug use to illustrate the value of this approach. This literature
suggests that social-influence-based strategies have been quite effective
under some conditions, but can be counterproductive under other conditions. This example underscores the value of identifying and evaluating
mediator and moderators variables in the drug-abuse prevention area. lt
is important to note that the example was limited to just one of the many
domains of drug-abuse prevention, but the process of high-potential
mediator and moderator analysis may be just as relevant across different
domains.
The recognition that drug-abuse prevention interventions often need
to be complex and multidimensional to address a specific prevention
problem, and may vary in effectiveness across participant characteristics,
contexts, and behavioral outcomes, should be helpful for the conceptual-
ization and evaluation of future prevention efforts. lt is my belief that a
careful investigation of the scientific literature in most prevention domains
will turn up at least some information helpful for identifying high-potential
mediators. Finally, future systematic external evaluations that involve
mediation and moderator analysis of intervention efforts promise to
increase our cumulative wisdom about how drug prevention interventions
work-and how to make them work better.
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