Autism Studies and Related Medical Conditions, January 2009 - TACA

increase in autism in the last decades, which parallels cumulative mercury
exposure, it was proposed that autism may be in part caused by mercury. We
review the evidence for this proposal. Several epidemiological studies failed to
find a correlation between mercury exposure through thimerosal, a preservative
used in vaccines, and the risk of autism. Recently, it was found that autistic
children had a higher mercury exposure during pregnancy due to maternal
dental amalgam and thimerosal-containing immunoglobulin shots. It was
hypothesized that children with autism have a decreased detoxification capacity
due to genetic polymorphism. In vitro, mercury and thimerosal in levels found
several days after vaccination inhibit methionine synthetase (MS) by 50%.
Normal function of MS is crucial in biochemical steps necessary for brain
development, attention and production of glutathione, an important antioxidative
and detoxifying agent. Repetitive doses of thimerosal leads to neurobehavioral
deteriorations in autoimmune susceptible mice, increased oxidative stress and
decreased intracellular levels of glutathione in vitro. Subsequently, autistic
children have significantly decreased level of reduced glutathione. Promising
treatments of autism involve detoxification of mercury, and supplementation of
deficient metabolites.
Nataf, R., C. Skorupka, et al. (2006). "Porphyrinuria in childhood autistic disorder:
implications for environmental toxicity." Toxicol Appl Pharmacol 214(2): 99-108.
To address a possible environmental contribution to autism, we carried out a
retrospective study on urinary porphyrin levels, a biomarker of environmental
toxicity, in 269 children with neurodevelopmental and related disorders referred
to a Paris clinic (2002-2004), including 106 with autistic disorder. Urinary
porphyrin levels determined by high-performance liquid chromatography were
compared between diagnostic groups including internal and external control
groups. Coproporphyrin levels were elevated in children with autistic disorder
relative to control groups. Elevation was maintained on normalization for age or
to a control heme pathway metabolite (uroporphyrin) in the same samples. The
elevation was significant (P < 0.001). Porphyrin levels were unchanged in
Asperger's disorder, distinguishing it from autistic disorder. The atypical molecule
precoproporphyrin, a specific indicator of heavy metal toxicity, was also elevated
in autistic disorder (P < 0.001) but not significantly in Asperger's. A subgroup
with autistic disorder was treated with oral dimercaptosuccinic acid (DMSA) with
a view to heavy metal removal. Following DMSA there was a significant (P =
0.002) drop in urinary porphyrin excretion. These data implicate environmental
toxicity in childhood autistic disorder.
Ng, F., M. Berk, et al. (2008). "Oxidative stress in psychiatric disorders: evidence base
and therapeutic implications." Int J Neuropsychopharmacol: 1-26.
Oxidative stress has been implicated in the pathogenesis of diverse disease
states, and may be a common pathogenic mechanism underlying many major
psychiatric disorders, as the brain has comparatively greater vulnerability to
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