Thimerosal: Autism’s Scapegoat
March 5, 2004
Scientific Method: Debunking Pseudoscience
Malia Bender

Thimerosal, a mercury-based preservative, has been keeping vaccine vials bacteria and fungus free since 1930. The need for thimerosal became apparent when people started experiencing bacterial infections after receiving vaccinations, due to the fact that the vaccines were kept in bottles that would have multiple doses drawn from them over the course of their short shelf lives. By adding thimerosal to the stock bottles, the vaccines would be kept clean of harmful microbes and preserved for a longer period of time. In recent years, a controversy has been raised concerning the true nature of thimerosal and its potentially harmful side effects. This paper will explore the misconception, primarily found among organizations comprised of parents with autistic children and Christian Scientists, that thimerosal causes autism.
1
According to the Stanford University Medical Center’s website, autism is classified as a pervasive developmental disorder (PDD) which is a complex neurodevelopmental disorder that typically appears during the first three years of life.
2 One known cause of autism is drug use, e.g. thalidomide, during pregnancy.
Other causes of autism are genetic, resulting from a mutation or nondisjunction during meiosis.
3 When nondisjunction occurs, a copy of a chromosome fails to
1 It is understandable that Christian Scientists would be a large proponent in the cause to eliminate vaccinations, as they do not believe in modern medicine, like immunizations, and doctors. They believe that illness is a “false-reality” that can be removed through prayer and positive thought with the help of
“Christian Science Practicioners.”
2 Lucile Packard Children’s Hospital. “Autism and Pervasive Developmental Disorders.” http://www.lpch.org/clinicalSpecialtiesServices/COE/BrainBehavior/Psychiatry/autismPervasiveDevelopm entalPsych.html
3 Laumonnier Frederic, Bonnet-Brilhault Frederique, et al. “X-Linked Mental Retardation and Autism are
Associated with a Mutation in the NLGN4 Gene, a Member of the Neuroligin Family.” American Journal of Human Genetics . Mar 2004, Vol. 74 Issue 3, p552.
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separate during cell division and upon fertilization the zygote carries 47 chromosomes instead of the normal 46. Usually this process results in a nonviable fertilized cell that is unable to continue cell division and aborts itself. However, when this occurs at the
21 st chromosome, the zygote is able to continue dividing and a fetus develops with
Trisomy 21, more commonly known as Down’s Syndrome, which will result in an autistic child. Children with autism are characterized by
“abnormal or impaired development in social interaction and communication, and limited repertoires of activities or interests. . .
Typically, they present with communication delays, both verbal and nonverbal, and some never develop language at all. Cognitive skills are also impaired; 75% to 80% of individuals with autism also meet the criteria for mental retardation.” 4
Children diagnosed with autism suffer from the disorder throughout their entire lifetimes and treatment is limited.
A reasonable starting point in the quest for the truth about thimerosal and its harmful, or benign, side effects is to look at why people insist that the two are related.
The first obvious reason is the coincidence of timing. Babies receive vaccinations in a series of rounds within the first 15 months after birth. This is a reasonable time to administer vaccinations since the developing baby has not yet encountered many pathogens, and thus has a weak immune system. Due to the baby’s inadequate immune system, vaccinations allow exposure to the antigens in a controlled
4 Goin Robin P, Myers Barbara J. “Infantile Autism: Moving Toward Earlier Detection.” Focus on
Autism & Other Developmental Disabilities . Spring 2004, Vol. 19 Issue 1. P 5.
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environment that will allow the baby to build resistance to the specific antigen. Since early signs of autism usually present themselves within the first three years of life, right around the time when the vaccinations are given, people might think that there is a correlation between the two.
Though it may seem reasonable for parents to recognize this overlapping of time as a link between autism and thimerosal, it is not a scientifically supported inference. This is because not all disorders or diseases manifest themselves immediately after contact. For instance, a person may contract the herpes simplex virus type two and not experience signs such as an outbreak for days, weeks, or even years. The virus has the ability to remain dormant until the host’s body presents a favorable environment for the virus to propagate itself. Genetic disorders can work in much the same way, therefore the fact that autism is usually first diagnosed at around the same time that the thimerosal-containing vaccinations are given is not evidence for a causal relationship.
Another reason why people might be inclined to assume that thimerosal causes autism is the view that the characteristics of children with autism are remarkably similar to those of children with mercury poisoning. The study by
Bernard et al. is the benchmark study for thimerosal critics. It is commonly referred to on websites by organizations of parents with autistic children as a source of scientific evidence that supports their claim that thimerosal caused their child’s
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autism.
5 First, a note about the credibility of the one “scientific” journal that published the Bernard et al. study: Medical Hypotheses.
6 Since this is not a widely referenced journal, a brief look at the journal’s website helps elucidate the quality of the journal as well as its intentions. For those unfamiliar with the journal, the “aims and scope” as listed on the publisher website is, “ Medical Hypotheses takes a deliberately different approach to peer review. Most contemporary practice tends to discriminate against radical ideas that conflict with current theory and practice.
Medical Hypotheses will publish radical ideas, so long as they are coherent and clearly expressed.” 7 With this being said and keeping in mind that the practice of scientific method and presentation of accurate data are not criteria for the journal to publish its submitted articles, a look at thimerosal protestors’ “scientific” support is in order.
The study claims to examine the signs and symptoms of autism and mercury poisoning and then states, “The parallels between the two diseases are so thorough as to suggest, based on total Hg injected into U.S. children, that many cases of autism are a form of mercury poisoning.” 8 A chart is presented in order to outline more clearly
5 Bernard S, Enayati A, Binstock T, Roger H, Redwood L, McGinnis W. “Autism: A Unique Type of
Mercury Poisoning.” April 3, 2000. Rev. April 21, 2000. Article can be accessed from the following website: http://www.jorsm.com/~binstock/thimerosal.htm
6 Bernard S, Enayati A, Binstock T, Roger H, Redwood L, McGinnis W. “Autism: A Novel Form of
Mercury Poisoning.” Medical Hypotheses . April 2001. Vol. 56. Issue 4. P 462-471.
7 Taken from the Medical Hypotheses publisher website http://www.harcourtinternational.com/journals/mehy/
8 Bernard S, Enayati A, Binstock T, Roger H, Redwood L, McGinnis W. “Autism: A Unique Type of
Mercury Poisoning.” April 3, 2000. Rev. April 21, 2000. P 5-7. Article can be accessed from the following website: http://www.jorsm.com/~binstock/thimerosal.htm
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the “parallels” and demonstrate how the shear volume of seemingly equal characteristics can be overwhelming and therefore convincing that the data is true.
The chart is displayed as appendix 1.
9 The table lists about 95 experimental findings that are almost identical in mercury poisoning and autism. Bernard et al. use exact wording between the two columns to stress that the signs and symptoms of both conditions are exactly the same. With such a seemingly comprehensive list of findings, one can only wonder why they neglected to include that mercury poisoning affects periphery nerves which would cause neuropathy in other organs and areas in addition to the brain, whereas only the brain is subject to impairment with autism.
Contrary to Bernard et al.’s findings, Drs. Karin B. Nelson and Margaret L.
Bauman published a commentary in the scientific journal, Pediatrics, which points out that the table from the Bernard et al. study “does not distinguish typical and characteristic manifestations of either disorder from the rare, unusual, and highly atypical.” 10 The table from Bernard et al. lumps every single possible sign of each disorder together in an attempt to show striking parallels between the two, however, a characteristic that is common for one may present itself only in extremely rare cases for the other. The article goes on to point out that mercury poisoning and autism do not share many of the characteristics outlined in the table. They included a table with complete documentation of experimentation and their findings. Their table is
9 Ibid. P 5-7.
10 Nelson, Karin B. Bauman, Margaret L. “Thimerosal and Autism?” Pediatrics . March 2003. Vol. III.
Issue 3. p.674.
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displayed in appendix 2.
11 It seems that there is quite a discrepancy between the two tables, however, Drs. Nelson and Bauman clearly address each finding in the article with a scientific experiment to support their conclusions.
12 No such scientific documentation is found in the Bernard et al. article, therefore it does not hold as scientific proof that autism and mercury poisoning produce the same results.
According to the commentary by Drs. Nelson and Bauman, “Bernard et al. state that ‘elevated mercury has been detected in biological samples of autistic patients,’ but unfortunately do not provide references. [Peers] found no paper published in the peer-reviewed literature that reported an abnormal body burden of mercury, or an excess of mercury in hair, urine, or blood.” 13 Bernard et al. do not offer any data in support of their claim that autistic patients’ biological samples contain high levels of mercury. In fact they admit otherwise when they state, “In each case we have tried to identify potential sources of exposure, although we have not been able to identify the exact amounts in some cases due to inadequate documentation.” 14 Without adequate documentation, their claim that the mercury from thimerosal remains in the body has not been proven.
In spite of the lack of evidence that thimerosal is responsible for autism, one might be convinced that the sheer amount of mercury injected into a baby is enough
11 Ibid. p.675.
12 Ibid. P.674-676.
13 Nelson, Karin B. Bauman, Margaret L. “Thimerosal and Autism?” Pediatrics . March 2003. Vol. III.
Issue 3. p.675
14 Bernard S, Enayati A, Binstock T, Roger H, Redwood L, McGinnis W. “Autism: A Unique Type of
Mercury Poisoning.” April 3, 2000. Rev. April 21, 2000. P 52. Article can be accessed from the following website: http://www.jorsm.com/~binstock/thimerosal.htm
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to cause harm. This, however, is not the case. There are two different compounds of mercury that need to be considered in the case for or against the danger of thimerosal: methyl mercury and ethyl mercury. Methyl mercury is the mercury that is studied in mercury poisoning research, not ethyl mercury. Sources of methyl mercury include contamination of fish due to waste from power plants seeping into water supplies and the major component of older tooth fillings. The only difference between the two compounds is just the absence of one carbon and two hydrogens, but it is significant.
Similarly, thalidomide, a drug used widely in Europe to alleviate the nausea that comes with pregnancy, comes in two forms. The only difference between the two is the spatial placement of one hydrogen atom, either slightly above or slightly below the plane of the molecule. However, one form effectively ameliorates morning sickness and the other causes severe birth defects.
15 Such a slight difference can have incredibly drastic effects in the body because enzymes and transport proteins in the body are extremely stereospecific. The wrong form of a chemical can throw a wrench in the body’s system and cause significant harm to the individual.
The fact that thimerosal is composed of ethyl mercury is important to note because the mechanism of uptake once in the body and elimination is quite different from that of methyl mercury in that “the passage of methyl mercury across the bloodbrain barrier is facilitated by an active transport mechanism, whereas the passage of
15 Voet Donald, Voet Judith G, Pratt Charlotte W. Fundamentals of Biochemistry. Upgrade edition. John
Wiley & Sons, Inc. P. 88.
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ethyl mercury into the brain does not have such a transport system and is further hindered by its larger molecular size and faster decomposition.” 16 Methyl mercury is much more toxic to humans than ethyl mercury because the body does have a way to transport methyl mercury into the brain. People speaking out against thimerosal make it a point to stress that the amount of “mercury” given to babies in vaccines is above the Environmental Protection Agency’s (EPA) guideline for safe amounts of
“mercury” uptake without stressing the fact that they are comparing two different compounds of mercury. The mercury used in the formulation of safe dosage guidelines in place by the EPA, Food and Drug Administration, and World Health
Organization is methyl mercury, the more toxic form. This means, “At between 12.5 and 25 mg mercury per vaccine dose, the infants may be receiving over 100 mg [of] ethyl mercury in the first 6 months of life.” 17 Even though the EPA recommends that the safe level of methyl mercury intake is 0.1 µg/kg body weight/day, the use of thimerosal is completely acceptable because it is shown that “the [ethyl mercury] levels in blood are much lower than the prescribed limits and that much of the ethyl mercury appears to be eliminated rapidly in feces. This study gives comforting reassurance about the safety of ethyl mercury as a preservative in childhood vaccines.” 18 When obtaining information about thimerosal and its link to autism it is
16 Nelson, Karin B. Bauman, Margaret L. “Thimerosal and Autism?” Pediatrics . March 2003. Vol. III.
Issue 3. p.676
17 Henderson, D C. “Heavy Metal.” Lancet.
November 30, 2002. Vol 360, Issue 9347. P. 1712.
18 Madsen Kreesten M, Lauritsne Marlene B, et al. “Thimerosal and the Occurrence of Autism: Negative
Ecological Evidence from Danish Population-Based Data.” Pediatrics. September 2003. Vol 112. P 604.
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important to note if the source makes the distinction between ethyl and methyl mercury. Most websites bashing thimerosal and vaccines in general only refer to
“mercury” levels which are usually referring to methyl mercury, the compound of mercury that is more harmful compared to ethyl form.
Another misguided attempt to cast doubt on the safety of thimerosal is to inquire about the continual rise in the number of cases of autism through the past couple of decades. Many people attribute the increase to the use of thimerosal and the increase in the number of vaccines that are currently required. Scientific data collected in various medical journals centered around children or autism, as well as from Denmark, does confirm that the number of cases of autism is increasing exponentially.
19 The connection between thimerosal and autism cannot be drawn from the fact that cases of autism are still increasing in number. If thimerosal were a cause of autism, then it would be reasonable to conclude that the number of cases of autism would also decrease after thimerosal was completely removed from all vaccinations administered to children. This is actually a testable hypothesis that was tested in 1992 when thimerosal was removed from the vaccinations given to children, but the graph of autism rates in Denmark from appendix 3 clearly shows that the number of cases of autism continues to increase significantly from 1992 to 1995 and
19 Henderson, D C. “Heavy Metal.” Lancet. November 30, 2002. Vol 360, Issue 9347. P. 1712.
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then again to 2000.
20 The increase in frequency of autism can be seen all over the world, including in the United States. This increase could possibly be due to the fact that doctors have devised more accurate methods of detecting autism. Autistic children that may have gone undiagnosed in the past are now being tested earlier and more thoroughly. Another possibility for the increase is that the criteria for diagnosis have evolved over the years and are now including a wider range of conditions under the umbrella of autism.
Conclusive evidence that thimerosal does not cause autism can be found in the
Denmark study. The purpose of the study was to determine whether or not there was a correlation between the people who received thimerosal-containing vaccinations with autism. The study was designed so that the researchers would look at the
Danish Psychiatric Central Research Register that records all psychiatric admissions since 1971, and all outpatient contacts in psychiatric departments in Denmark since
1995.
21 Since everyone in Denmark has a personal identification number, much like the social security number in the United States, the researchers would be able to keep track of people diagnosed with autism. They were able to keep track of how many cases of autism were reported every year from 1971 to 2000 and watch for a change subsequent to the removal of thimerosal from their vaccines. An increase in the
20 Madsen Kreesten M, Lauritsen Marlen B, et al. Pediatrics . September 2003. Vol III. Issue 3. p 605.
21 Ibid. p 604.
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incidence of autism was observed throughout the entire study, which would point to the conclusion that there is no causal relationship between thimerosal and autism.
The Bernard et al. study is an important source for anti-thimerosal advocates.
As always, even scientific data should be closely examined for under-the-table funding from certain groups, e.g. a law firm wanting to take vaccine manufacturers to court. At the end of the article published by Bernard et al., Ayda Halker is listed as a person that they would like to thank for her “important contributions.” 22 She is also the founder and president of AutismOnline.org as well as a parent of a child with autism and sister to a young man who has autism.
23 This could be seen as a conflict of interest since she is heavily influenced by autism and its effects, yet an avid supporter of Bernard. Scientific research should be an objective process with sheer motivation of uncovering the truth, not necessarily to reach conclusions that were previously expected. The Bernard study does not invoke a feeling of confidence in its findings when the research supporters are revealed because of the obvious intention to “prove” that thimerosal causes autism.
The published Denmark study also includes a section for acknowledgments at the end of the article. The authors state that their research was funded by a grant from the Danish National Research Foundation and supported by the Stanley
Medical Research Institute. They also include that no funding sources were involved
22 Bernard S, Enayati A, Binstock T, Roger H, Redwood L, McGinnis W. “Autism: A Unique Type of
Mercury Poisoning.” April 3, 2000. Revision April 21, 2000. P 62. Article can be accessed from http://www.jorsm.com/~binstock/thimerosal.htm
23 Information obtained from http://www.icdri.org/ASH.htm
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in the study design.
24 Since the funding came from an unbiased source, as opposed to an individual who has already established a firm opinion on what the outcome should be, the data presented by this study can be accepted with less suspicion.
In 1997, The Food and Drug Administration (FDA) Modernization Act of 1997 called for the FDA to review and assess the risk of all mercury containing food and drugs. As part of this effort, the FDA conducted a review of mercury content in vaccines.
25 As the vaccines began to be reviewed, Christian Scientists and others against immunizations saw their chance to become even more vocal in the protest.
Pressure from these groups helped push the American Academy of Pediatrics (AAP) and the United States Public Health Service (PHS) toward issuing a recommendation to remove thimerosal from vaccines as a precaution. Since it is cheaper to manufacture single use vials now and there are more non-mercury-based preservatives available, the need for thimerosal is virtually eliminated. The decision to remove thimerosal from vaccines given to infants has inevitably caused parents to consider that it was harmful in the first place.
When glancing at the just the raw numbers of amounts of ethyl mercury in thimerosal and guidelines for methyl mercury set by government agencies, it is understandable to question the safety of the vaccines. The Center for Disease Control and Prevention website states that “A review conducted by the Food and Drug
24 Madsen Kreesten M, Lauritsen Marlen B, et al. Pediatrics . September 2003. Vol III. Issue 3. p 605.
25 Taken from the Center for Disease Control and Prevention website http://www.cdc.gov/nip/vacsafe/concerns/thimerosal/faqs-thimerosal.htm
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Administration (FDA) concluded that the use of thimerosal as a preservative in vaccines might result in the intake of mercury during the first 6 months of life that exceeds the Environmental Protection Agency (EPA), but not the FDA, the Agency for Toxic Substances and Disease Registry (ATSDR), or the World Health
Organization (WHO) guidelines for methyl mercury intake.” 26 It is important to keep in mind that the ethyl mercury in vaccines cannot be compared with the methyl mercury limits set by the above organizations because they differ in degree of toxicity: with methyl mercury being more toxic than ethyl mercury.
Also, it is worth noting the purpose for these federal guidelines as well as the means by which they are determined. The guidelines are in place in order to recommend a safe mercury exposure level for a woman who is pregnant in order to prevent harm to a fetus’s developing brain. A developing fetus in utero is more susceptible to mercury poisoning than a fully developed infant because it’s central nervous system has not yet completed development. Also, it’s liver and kidneys are not functioning to their fullest capacity and break down the mercury less efficiently.
The key point here is that these limits are in place for a developing fetus in the womb, not a fully developed infant. Another point to keep in mind is what exactly the
“recommended allowable daily exposure” means. This is a value for the estimated maximum amount of daily oral intakes of methyl mercury during pregnancy that
26 Taken from the Center for Disease Control and Prevention website http://www.cdc.gov/nip/vacsafe/concerns/thimerosal/faqs-thimerosal.htm
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“were not associated with measurable adverse outcomes in their children.” 27 These values only reflect the estimated amount of methyl mercury that could elicit detectable change in the fetus, not measurable harm to the fetus. Even if the ethyl mercury was as toxic as the methyl mercury used to set these guidelines, the dosage in the vaccines is still less than the FDA’s recommendation and the FDA is the agency responsible for setting the limit in vaccines, not the EPA who has a much more conservative limit than any of the other organizations.
With the understanding that there is no evidence supporting a link between thimerosal and the incidence of autism, the new question is “Why do so many people continue to insist that thimerosal causes autism?” The question can easily be answered by examining why some people willingly spend thousands of dollars for a one-hour session of twenty questions with a “psychic.” People need closure and hope after dealing with a traumatic experience. Having a child with autism is no doubt a profound and constant emotional and financial burden. Though autistic children can be as loving and rewarding as any other child, they do demand a copious amount of attention and care. Parents of autistic children are searching for answers as to why their child happened to have the disorder. It is appealing to blame the vaccine manufacturers who are large nameless entities that can accept the blame for their child’s abnormality. Their large bank accounts sweeten the pot and lead to the next
27 Taken from the American Academy of Pediatrics: Thimerosal in Vaccines – an Interim Report to
Clinicians on the Indiana State Department of Health website http://www.state.in.us/isdh/programs/immunization/thimerosal.htm
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logical step in justice for their child: lawsuits. This is not to say that parents are only after the manufactures for money, although the increase in volume of thimerosal cases may point to otherwise. On most anti-thimerosal websites is a link to a law firm, specializing in thimerosal cases. In a world where every person believes he is entitled to zero-risk healthcare, thimerosal is perfect to blame. Now that vaccines come in single-use vials, eliminating the need for thimerosal, what will be the next scapegoat?
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Appendix 1: Summary Comparison of Characteristics of Autism & Mercury
Poisoning 28
Psychiatric
Disturbances
Speech,
Language &
Hearing
Deficits
Sensory
Abnormalities
Mercury Poisoning
Social deficits, shyness, social withdrawal
Autism
Social deficits, social withdrawal, shyness
Depression, mood swings; mask face
Anxiety
Schizoid tendencies, OCD traits
Depressive traits, mood swings; flat affect
Anxiety
Schizophrenic & OCD traits; repetitiveness
Lack of eye contact, avoids conversation Lacks eye contact, hesitant to engage others
Irrational fears Irrational fears
Irritability, aggression, temper tantrums Irritability, aggression, temper tantrums
Impaired face recognition Impaired face recognition
Loss of speech, failure to develop speech Delayed language, failure to develop speech
Dysarthria; articulation problems
Speech comprehension deficits
Dysarthria; articulation problems
Speech comprehension deficits
Verbalizing & word retrieval problems Echolalia; word use & pragmatic errors
Sound sensitivity Sound sensitivity
Hearing loss; deafness in very high doses
Mild to profound hearing loss
Poor performance on language IQ tests Poor performance on verbal IQ tests
Abnormal sensation in mouth & extremities
Sound sensitivity
Abnormal touch sensations; touch aversion
Abnormal sensation in mouth & extremities
Sound sensitivity
Abnormal touch sensations; touch aversion
Vestibular abnormalities
Motor Disorders Involuntary jerking movements – arm flapping, ankle jerks, myoclonal jerks, choreiform movements, circling, rocking
Vestibular abnormalities
Stereotyped movements - arm flapping, jumping, circling, spinning, rocking; myoclonal jerks; choreiform movements
Deficits in eye-hand coordination; limb apraxia; intention tremors
Gait impairment; ataxia – from incoordination & clumsiness to inability to walk, stand, or sit; loss of motor control
Poor eye-hand coordination; limb apraxia; problems with intentional movements
Abnormal gait and posture, clumsiness and incoordination; difficulties sitting, lying, crawling, and walking
28 Bernard S, Enayati A, Binstock T, Roger H, Redwood L, McGinnis W. “Autism: A Unique Type of
Mercury Poisoning.” April 3, 2000. Revision April 21, 2000. P 62. Article can be accessed from http://www.jorsm.com/~binstock/thimerosal.htm
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Cognitive
Impairments
Unusual
Behaviors
Visual
Impairments
Physical
Disturbances
Difficulty in chewing or swallowing
Unusual postures; toe walking
Borderline intelligence, mental retardation - some cases reversible
Difficulty chewing or swallowing
Unusual postures; toe walking
Borderline intelligence, mental retardation
- sometimes "recovered"
Poor concentration, attention, response inhibition
Uneven performance on IQ subtests
Poor concentration, attention, shifting attention
Uneven performance on IQ subtests
Verbal IQ higher than performance IQ Verbal IQ higher than performance IQ
Poor short term, verbal, & auditory memory
Poor short term, auditory & verbal memory
Poor visual and perceptual motor skills, impairment in simple reaction time
Difficulty carrying out complex commands
Word-comprehension difficulties
Deficits in understanding abstract ideas
& symbolism; degeneration of higher mental powers
Poor visual and perceptual motor skills, lower performance on timed tests
Difficulty carrying out multiple commands
Word-comprehension difficulties
Deficits in abstract thinking & symbolism, understanding other’s mental states, sequencing, planning & organizing
Stereotyped sniffing (rats)
ADHD traits
Agitation, unprovoked crying, grimacing, staring spells
Sleep difficulties
Eating disorders, feeding problems
Stereotyped, repetitive behaviors
ADHD traits
Agitation, unprovoked crying, grimacing, staring spells
Sleep difficulties
Eating disorders, feeding problems
Self injurious behavior, e.g. head banging Self injurious behavior, e.g. head banging
Poor eye contact, impaired visual fixation
“Visual impairments,” blindness, nearsightedness, decreased visual acuity
Light sensitivity, photophobia
Blurred or hazy vision
Constricted visual fields
Increase in cerebral palsy; hyper- or hypo-tonia; abnormal reflexes; decreased muscle strength, especially upper body; incontinence; problems chewing, swallowing, salivating
Rashes, dermatitis/dry skin, itching; burning
Autonomic disturbance: excessive sweating, poor circulation, elevated heart rate
Poor eye contact, problems in joint attention
“Visual impairments”; inaccurate/slow saccades; decreased rod functioning
Over-sensitivity to light
Blurred vision
Not described
Increase in cerebral palsy; hyper- or hypotonia; decreased muscle strength, especially upper body; incontinence; problems chewing and swallowing
Rashes, dermatitis, eczema, itching
Autonomic disturbance: unusual sweating, poor circulation, elevated heart rate
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Gastro-intestinal Gastroenteritis, diarrhea; abdominal pain, constipation, “colitis”
Disturbances Anorexia, weight loss, nausea, poor appetite
Lesions of ileum & colon; increased gut permeability
Abnormal
Biochemistry
Immune
Dysfunction
CNS Structural
Pathology
Inhibits dipeptidyl peptidase IV, which cleaves casomorphin
Binds -SH groups; blocks sulfate transporter in intestines, kidneys
Has special affinity for purines & pyrimidines
Reduces availability of glutathione, needed in neurons, cells & liver to detoxify heavy metals
Causes significant reduction in glutathione peroxidase and glutathione reductase
Disrupts mitochondrial activities, especially in brain
Sensitivity due to allergic or autoimmune reactions; sensitive individuals more likely to have allergies, asthma, autoimmune-like symptoms, especially rheumatoid-like ones
Can produce an immune response in
CNS
Causes brain/MBP autoantibodies
Causes overproduction of Th2 subset; kills/inhibits lymphocytes, T-cells, and monocytes; decreases NK T-cell activity; induces or suppresses IFNg & IL-2
Selectively targets brain areas unable to detoxify or reduce Hg-induced oxidative stress
Damage to Purkinje and granular cells
Accummulates in amygdala and hippocampus
Causes abnormal neuronal cytoarchitecture; disrupts neuronal migration & cell division; reduces
NCAMs
Progressive microcephaly
Diarrhea, constipation, gaseousness, abdominal discomfort, colitis
Anorexia; feeding problems/vomiting
Leaky gut syndrome
Inadequate endopeptidase enzymes needed for breakdown of casein & gluten
Low sulfate levels
Purine & pyrimidine metabolism errors lead to autistic features
Low levels of glutathione; decreased ability of liver to detoxify heavy metals
Abnormal glutathione peroxidase activities in erythrocytes
Mitochondrial dysfunction, especially in brain
More likely to have allergies and asthma; familial presence of autoimmune diseases, especially rheumatoid arthritis; IgA deficiencies
On-going immune response in CNS
Brain/MBP autoantibodies present
Skewed immune-cell subset in the Th2 direction; decreased responses to T-cell mitogens; reduced NK T-cell function; increased IFNg & IL-12
Specific areas of brain pathology; many functions spared
Damage to Purkinje and granular cells
Pathology in amygdala and hippocampus
Neuronal disorganization; increased neuronal cell replication, increased glial cells; depressed expression of NCAMs
Progressive microcephaly and
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Abnormalities in
Neuro-chemistry
EEG
Abnormalities/
Epilepsy
Brain stem defects in some cases
Prevents presynaptic serotonin release
& inhibits serotonin transport; causes calcium disruptions
Alters dopamine systems; peroxidine deficiency in rats resembles mercurialism in humans
Elevates epinephrine & norepinephrine levels by blocking enzyme that degrades epinephrine
Elevates glutamate
Leads to cortical acetylcholine deficiency; increases muscarinic receptor density in hippocampus & cerebellum
Causes demyelinating neuropathy
Causes abnormal EEGs, epileptiform activity
Causes seizures, convulsions
Causes subtle, low amplitude seizure activity
Population Effects more males than females
Charact-eristics At low doses, only affects those geneticially susceptible
First added to childhood vaccines in
1930s
Exposure levels steadily increased since
1930s with rate of vaccination, number of vaccines
Exposure occurs at 0 - 15 months; clinical silent stage means symptom emergence delayed; symptoms emerge gradually, starting with movement & sensation macrocephaly
Brain stem defects in some cases
Decreased serotonin synthesis in children; abnormal calcium metabolism
Possibly high or low dopamine levels; positive response to peroxidine (lowers dopamine levels)
Elevated norepinephrine and epinephrine
Elevated glutamate and aspartate
Cortical acetylcholine deficiency; reduced muscarinic receptor binding in hippocampus
Demyelination in brain
Abnormal EEGs, epileptiform activity
Seizures; epilepsy
Subtle, low amplitude seizure activities
Male:female ratio estimated at 4:1
High heritability - concordance for MZ twins is 90%
First "discovered" among children born in
1930s
Prevalence of autism has steadily increased from 1 in 2000 (pre1970) to 1 in 500 (early
1990s), higher in 2000.
Symptoms emerge from 4 months to 2 years old; symptoms emerge gradually, starting with movement & sensation
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Appendix 2 Characteristic Findings in Autism and in Mercury Poisoning 29
Autism Mercurism
Motor
Vision
Speech
Stereotypies
No abnormality
Delay, echolalia
Sensory Hyper-responsiveness
Ataxia, dysarthria
Constricted visual fields
Dysarthria
Peripheral neuropathy
Psychiatric Socially aloof, insistence on sameness
Toxic psychosis; in mild cases, nonspecific depression, anxiety
Head size Large Small
Appendix 3: Autism Rates in Denmark 30
Autism rates began to climb in
1991, but continued to rise through 2000, even after thimerosal use was discontinued in 1992.
29 Nelson, Karin B. Bauman, Margaret L. “Thimerosal and Autism?” Pediatrics . March 2003. Vol. III.
Issue 3. p.674.
30 Madsen Kreesten M, Lauritsen Marlen B, et al. Pediatrics . September 2003. Vol III. Issue 3. p 605.
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