According to the diathesis stress model, a genetic predisposition for developing autism is not sufficient all by itself for someone to develop autism. Some form of stressor would also need to occur that transformed the latent predisposition into an actual active form of the illness. A wide variety of environmental stressors, including various environmental pollutants, toxins, viruses and the like, have been proposed to be capable of performing such an activating role. Research on the environmental causes of autism is ongoing and new developments continue to emerge. No one environmental cause has been identified, however, and many researchers believe that there may be multiple pathways through which autism can occur.
Vaccines and Mercury Poisoning.
One particularly controversial theory suggested that autism may be created in vulnerable people through exposure to a mercury compound (Thimerosal) formerly used as a preservative in normal childhood vaccines such as the MMR (Measles, Mumps and German Measles/Rubella) vaccine. The supposed link between autism and vaccination was fueled by simple but inconclusive observation1. First, many children developed symptoms of autism during the same period of time as they received MMR vaccines. Second, mercury is a known toxic compound that can result in neurological damage in children and adults that appears symptomatically similar to autism. Despite the compelling simplicity of the alleged connection between autism and Thimerosal/mercury, the available research suggests that there is no reliable relationship between them. Certainly, exposure to mercury is not in any child's interest, but the mercury compound Thimerosal does not appear to cause autism all by itself. Thimerosal has not been used as a preservative for vaccines since the year 2000. However, vaccines with the preservative may still possibly be in circulation.
Parents looking to avoid mercury exposure need to know that there are numerous other sources of environmental mercury contamination besides Thimerosal. Mercury is a common industrial pollutant. It is found in disinfectants and it is frequently a byproduct of electric power generation. You can get information on mercury and other sources of pollution in your area by entering your zip code into Scorecard.Com (http://scorecard.com), which will provide you with an in-depth report for free.
Though mercury pollution is a serious problem, the Environmental Protection Agency (EPA) has not been in a political position recently to do much regulating of mercury pollution. If you don't like that situation, consider supporting environmental advocacy groups like Natural Resources Defense Council (http://www.nrdc.org/health/effects/mercury/index.asp) or SaveTheCleanAirAct.Org (http://www.savethecleanairact.org/) that are pushing for reform in this area.
One of the best simple ways to reduce the amount of mercury your family is exposed to, is to reduce the amount of ocean-going fish you eat. Mercury concentrates in the flesh of various long-lived ocean fish such as shark, salmon, swordfish and tuna. People who eat those fish in any form ingest high levels of mercury without knowing it. Avoiding eating those fish can result in your eating less mercury. More information about mercury contamination in fish, and a calculator that can help you estimate your family's risk can be found here (http://www.nrdc.org/health/effects/mercury/protect.asp).
1 A British Medical Journal (BMJ) article published in January 2011 describes that the original research study that proposed this controversial theory has been proven to be fraudulent. In 2004, 10 of the study's coauthors made a partial retraction of the research. However, the lead author, Andrew Wakefield, continued to state that the research was true. In 2011, the United Kingdom's General Medical Council (GMC) officially charged Wakefield and two of the co-authors, John Walker-Smith and Simon Murch. Walker-Smith was found guilty of misconduct and Wakefield was found guilty of dishonesty concerning the study’s admissions criteria, its funding by the Legal Aid Board, and his statements about it afterwards. The GMC officially stripped Wakefield of his clinical and academic credentials. The BMJ article discusses that during the GMC's investigation, it was proven that "not one of the 12 cases reported in the 1998 Lancet paper was free of misrepresentation or undisclosed alteration, and that in no single case could the medical records be fully reconciled with the descriptions, diagnoses, or histories published in the journal."