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Thimerosal: Autism’s Scapegoat
March 5, 2004
Scientific Method: Debunking PseudoscienceMalia 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
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/autismPervasiveDevelopmentalPsych.html3 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.
2
When nondisjunction occurs, a copy of a chromosome fails to 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 21st 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 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.
3
exposure to the antigens in a controlled 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
4
evidence that supports their claim that thimerosal caused their child’s
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
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.htm6 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.harcourt-international.com/journals/mehy/
5
poisoning.” 8 A chart is presented in order to outline more clearly 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
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.htm9 Ibid. P 5-7. 10 Nelson, Karin B. Bauman, Margaret L. “Thimerosal and Autism?” Pediatrics. March 2003. Vol. III. Issue 3. p.674.
6
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 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
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
7
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 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 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.htm15 Voet Donald, Voet Judith G, Pratt Charlotte W. Fundamentals of Biochemistry. Upgrade edition. John Wiley & Sons, Inc. P. 88.
8
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 blood-brain barrier is
facilitated by an active transport mechanism, whereas the passage of
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
16 Nelson, Karin B. Bauman, Margaret L. “Thimerosal and Autism?” Pediatrics. March 2003. Vol. III. Issue 3. p.676
9
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 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 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 604.19 Henderson, D C. “Heavy Metal.” Lancet. November 30, 2002. Vol 360, Issue 9347. P. 1712.
10
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 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 20 Madsen Kreesten M, Lauritsen Marlen B, et al. Pediatrics. September 2003. Vol III. Issue 3. p 605.
11
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 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 21 Ibid. p 604.22 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.htm23 Information obtained from http://www.icdri.org/ASH.htm
12
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 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 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
13
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 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.
26 Taken from the Center for Disease Control and Prevention website http://www.cdc.gov/nip/vacsafe/concerns/thimerosal/faqs-thimerosal.htm
14
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 “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.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
15
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 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?
16
Appendix 1: Summary Comparison of Characteristics of Autism
& Mercury Poisoning28
Mercury Poisoning AutismPsychiatric Social deficits, shyness, social
withdrawalSocial deficits, social withdrawal, shyness
Disturbances Depression, mood swings; mask face
Depressive traits, mood swings; flat affect
Anxiety AnxietySchizoid tendencies, OCD traits Schizophrenic & OCD traits;
repetitivenessLacks eye contact, hesitant to engage others
Lack of eye contact, avoids conversation
Irrational fears Irrational fearsIrritability, aggression, temper tantrums
Irritability, aggression, temper tantrums
Impaired face recognition Impaired face recognition
Speech, Loss of speech, failure to develop speech
Delayed language, failure to develop speech
Language & Dysarthria; articulation problems Dysarthria; articulation problems Hearing Speech comprehension deficits Speech comprehension deficitsDeficits Verbalizing & word retrieval
problemsEcholalia; word use & pragmatic errors
Sound sensitivity Sound sensitivityHearing loss; deafness in very high doses
Mild to profound hearing loss
Poor performance on language IQ tests
Poor performance on verbal IQ tests
Sensory Abnormal sensation in mouth & extremities
Abnormal sensation in mouth & extremities
Abnormalities Sound sensitivity Sound sensitivityAbnormal touch sensations; touch aversion
Abnormal touch sensations; touch aversion
Vestibular abnormalities Vestibular abnormalities
Motor Disorders
Involuntary jerking movements – arm flapping, ankle jerks, myoclonal jerks, choreiform movements, circling, rocking
Stereotyped movements - arm flapping, jumping, circling, spinning, rocking; myoclonal jerks; choreiform movements
Deficits in eye-hand coordination; limb apraxia; intention tremors
Poor eye-hand coordination; limb apraxia; problems with intentional movements
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
17
Gait impairment; ataxia – from incoordination & clumsiness to inability to walk, stand, or sit; loss of motor control
Abnormal gait and posture, clumsiness and incoordination; difficulties sitting, lying, crawling, and walking
Difficulty in chewing or swallowing
Difficulty chewing or swallowing
Unusual postures; toe walking Unusual postures; toe walking
Cognitive Impairments
Borderline intelligence, mental retardation - some cases reversible
Borderline intelligence, mental retardation - sometimes "recovered"
Poor concentration, attention, response inhibition
Poor concentration, attention, shifting attention
Uneven performance on IQ subtests
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
Poor visual and perceptual motor skills, lower performance on timed tests
Difficulty carrying out complex commands
Difficulty carrying out multiple commands
Word-comprehension difficulties Word-comprehension difficultiesDeficits in understanding abstract ideas & symbolism; degeneration of higher mental powers
Deficits in abstract thinking & symbolism, understanding other’s mental states, sequencing, planning & organizing
Unusual Stereotyped sniffing (rats) Stereotyped, repetitive behaviorsBehaviors ADHD traits ADHD traits
Agitation, unprovoked crying, grimacing, staring spells
Agitation, unprovoked crying, grimacing, staring spells
Sleep difficulties Sleep difficultiesEating disorders, feeding problems
Eating disorders, feeding problems
Self injurious behavior, e.g. head banging
Self injurious behavior, e.g. head banging
Visual Poor eye contact, impaired visual fixation
Poor eye contact, problems in joint attention
Impairments “Visual impairments,” blindness, near-sightedness, decreased visual acuity
“Visual impairments”; inaccurate/slow saccades; decreased rod functioning
Light sensitivity, photophobia Over-sensitivity to lightBlurred or hazy vision Blurred visionConstricted visual fields Not described
18
Physical Disturbances
Increase in cerebral palsy; hyper- or hypo-tonia; abnormal reflexes; decreased muscle strength, especially upper body; incontinence; problems chewing, swallowing, salivating
Increase in cerebral palsy; hyper- or hypotonia; decreased muscle strength, especially upper body; incontinence; problems chewing and swallowing
Rashes, dermatitis/dry skin, itching; burning
Rashes, dermatitis, eczema, itching
Autonomic disturbance: excessive sweating, poor circulation, elevated heart rate
Autonomic disturbance: unusual sweating, poor circulation, elevated heart rate
Gastro-intestinal
Gastroenteritis, diarrhea; abdominal pain, constipation, “colitis”
Diarrhea, constipation, gaseousness, abdominal discomfort, colitis
Disturbances Anorexia, weight loss, nausea, poor appetite
Anorexia; feeding problems/vomiting
Lesions of ileum & colon; increased gut permeability
Leaky gut syndrome
Inhibits dipeptidyl peptidase IV, which cleaves casomorphin
Inadequate endopeptidase enzymes needed for breakdown of casein & gluten
Abnormal Biochemistry
Binds -SH groups; blocks sulfate transporter in intestines, kidneys
Low sulfate levels
Has special affinity for purines & pyrimidines
Purine & pyrimidine metabolism errors lead to autistic features
Reduces availability of glutathione, needed in neurons, cells & liver to detoxify heavy metals
Low levels of glutathione; decreased ability of liver to detoxify heavy metals
Causes significant reduction in glutathione peroxidase and glutathione reductase
Abnormal glutathione peroxidase activities in erythrocytes
Disrupts mitochondrial activities, especially in brain
Mitochondrial dysfunction, especially in brain
Immune Dysfunction
Sensitivity due to allergic or autoimmune reactions; sensitive individuals more likely to have allergies, asthma, autoimmune-like symptoms, especially rheumatoid-like ones
More likely to have allergies and asthma; familial presence of autoimmune diseases, especially rheumatoid arthritis; IgA deficiencies
Can produce an immune response in CNS
On-going immune response in CNS
Causes brain/MBP autoantibodies Brain/MBP autoantibodies presentCauses overproduction of Th2 subset; kills/inhibits lymphocytes, T-cells, and monocytes; decreases NK T-cell activity; induces or suppresses IFNg & IL-2
Skewed immune-cell subset in the Th2 direction; decreased responses to T-cell mitogens; reduced NK T-cell function; increased IFNg & IL-12
CNS Structural Selectively targets brain areas Specific areas of brain pathology;
19
Pathology unable to detoxify or reduce Hg-induced oxidative stress
many functions spared
Damage to Purkinje and granular cells
Damage to Purkinje and granular cells
Accummulates in amygdala and hippocampus
Pathology in amygdala and hippocampus
Causes abnormal neuronal cytoarchitecture; disrupts neuronal migration & cell division; reduces NCAMs
Neuronal disorganization; increased neuronal cell replication, increased glial cells; depressed expression of NCAMs
Progressive microcephaly Progressive microcephaly and macrocephaly
Brain stem defects in some cases Brain stem defects in some cases
Abnormalities in Neuro-chemistry
Prevents presynaptic serotonin release & inhibits serotonin transport; causes calcium disruptions
Decreased serotonin synthesis in children; abnormal calcium metabolism
Alters dopamine systems; peroxidine deficiency in rats resembles mercurialism in humans
Possibly high or low dopamine levels; positive response to peroxidine (lowers dopamine levels)
Elevates epinephrine & norepinephrine levels by blocking enzyme that degrades epinephrine
Elevated norepinephrine and epinephrine
Elevates glutamate Elevated glutamate and aspartateLeads to cortical acetylcholine deficiency; increases muscarinic receptor density in hippocampus & cerebellum
Cortical acetylcholine deficiency; reduced muscarinic receptor binding in hippocampus
Causes demyelinating neuropathy
Demyelination in brain
EEG Causes abnormal EEGs, epileptiform activity
Abnormal EEGs, epileptiform activity
Abnormalities/ Causes seizures, convulsions Seizures; epilepsyEpilepsy Causes subtle, low amplitude
seizure activitySubtle, low amplitude seizure activities
Population Effects more males than females Male:female ratio estimated at 4:1Charact-eristics
At low doses, only affects those geneticially susceptible
High heritability - concordance for MZ twins is 90%
First added to childhood vaccines in 1930s
First "discovered" among children born in 1930s
Exposure levels steadily increased since 1930s with rate of vaccination, number of vaccines
Prevalence of autism has steadily increased from 1 in 2000 (pre1970) to 1 in 500 (early 1990s), higher in 2000.
Exposure occurs at 0 - 15 months; clinical silent stage means symptom emergence delayed; symptoms emerge gradually, starting with
Symptoms emerge from 4 months to 2 years old; symptoms emerge gradually, starting with movement & sensation
20
movement & sensation
21
Appendix 2 Characteristic Findings in Autism and in Mercury Poisoning29
Autism Mercurism
Motor Stereotypies Ataxia, dysarthriaVision No abnormality Constricted visual fieldsSpeech Delay, echolalia DysarthriaSensory Hyper-responsiveness Peripheral neuropathyPsychiatric Socially aloof,
insistence on samenessToxic psychosis; in mild cases, nonspecific depression, anxiety
Head size Large Small
Appendix 3: Autism Rates in Denmark30
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.
22
Autism rates began to climb in 1991, but continued to rise through 2000, even after thimerosal use was discontinued in 1992.