Autism Spectrum Disorders And Thimerosal In Vaccines

Autism Spectrum Disorders and Thimerosal in Vaccines

PROBLEM

Thimerosal (organic mercury compound) has been used as a preservative in vaccines since 1930. The recent increase in incidence of autism spectrum disorders (ASDs) along with other pervasive developmental disorders (PDDs) and the theoretical relationship to mercury toxicity has led some to question the safety of many mercury-containing vaccines. To evaluate any such relationship, we systematically reviewed literature from several perspectives to identify any association or correlation between thimerosal and ASDs or other PDDs.

Satya K. Gutta 1 and Dan R. Denson 2 1 [Graduate Student, Health and Human Performance, McNeese State University, P.O. Box 91855 HHP, Lake Charles, LA-70609], 2 [Professor, Department of Health and Human Performance, McNeese State University, P.O. Box 91855 HHP, Lake Charles, LA-70609] METHODS A search was conducted on the World Wide Web to identify published studies between 1900 and 2008. Search engines used included Metacrawler, Webfeat, Google, and Pubmed. Key words were thimerosal, thiomersal, autism, ASD, vaccination, immunization, mercury toxicity, methyl mercury, ethyl mercury, and neurotoxicity. DSM-4 was consulted for definitions of autism, ASDs, PPDs, and related terms. All original articles and some abstracts that addressed the link between thimerosal, ASDs, PPDs or other neuro-developmental disorders were included. RESULTS Sixteen epidemiological studies that met the selection criteria were critically reviewed. Other papers reported research in the areas of biochemistry, pharmaco-toxicokinetics, genetics, and immunology. Confounding variables, limitations, outcomes and associations were reported in a few studies. Some studies found a positive association between methyl mercury exposure and certain neurological disorders, particularly attention deficit disorder. Some studies failed to differentiate between methyl mercury toxicity and the thimerosal version of ethyl mercury. Most of the epidemiological studies found no relationships between the variables in question. The genetics studies and immunology studies suggested genetic predisposition combined with environmental factors playing the major roles in the etiology of autism. The findings from PET and CT scans of brains of autistic children clearly reject any association between autism and thimerosal. CONCLUSION While the hypothesis that exposure to thimerosal-containing vaccines could be associated with ASDs and certain neuro-developmental disorders is biologically plausible, the evidence seems inadequate to either accept or reject a causal relationship. Additional studies are needed to establish or reject a causal relationship. For additional information please contact: [Dr. Dan R. Denson] [Department of Health and Human Performance] [McNeese State University] [ddenson@mcneese.edu]

REFERENCES

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Department of Health and Human Services, (June 2007). Retrieved May 12, 2008, from http://vaers.hhs.gov/search/README.txt

Fombonne, E. , Zakarian, R. , Bennett, A. , Meng, L. , Heywood, M. D. (2006). Pervasive developmental disorders in montreal, quebec, Canada: Prevalence and links with immunizations. Pediatrics , 118 , e139-e150.

Kirby, D. (2008, February 25).Government concedes vaccine-autism case in federal court- now what? The Huffington Post. Retrieved April,30,2008,from http :// www.huffingtonpost.com/ david- kirby/government-concedes- vacci_b_88323.html

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National Institute of Mental Health, (February 2007). Research into causes and treatment of autism spectrum disorders. Retrieved May 1, 2008

from http://www.nimh.nih.gov/health/publication s/autism/research.shtml

Figure 4. Children with ASDs in Interactive Autism Network (IAN) Research – Current Diagnosis Figure 1. Characteristics of Autism Spectrum Disorder (ASD) Source: St. Gabriel's Special Needs Website