1. Causes of Autism There is no known single cause for autism, and no know really knows for sure what the cause is. Experts say it is most likely the result of a combination of genetic and environmental factors. Some experts say it is caused by abnormalities in the brain, which brain scans have shown differences in the shape and structure of the brain. In many families, there appears to be a pattern of autism or related disabilities which further supports a genetic basis to the disorder. While no gene has been identified as causing autism, researchers are searching for irregular segments of genetic code that autistic children may have inherited.

2. It also appears that some children are born with a susceptibility to autism, but researchers do not know what could “trigger” autism to develop. Autism tends to occur more frequently than expected among individuals who have certain medical conditions, including fragile X syndrome, tuberous sclerosis, and untreated phenylketonuria (PKU). Still, other researchers are investigating the problems during pregnancy or delivery as well as environmental factors such as viral infection, metabolic imbalances, and exposure to environmental chemicals. In early 2002, the agency for Toxic Substances and Disease Registry (ATSDR) prepared a literature review of hazardous chemicals and autism and found no compelling evidence for an association. So the ingestion of harmful substances during a pregnancy is not associated with an increase in chances of autism. However, there was very limited research and more needs to be done.

3. The Controversy The question of what causes autism is highly controversial. Recent books, articles, and TV programs have raised awareness- and heated up the argument. One argument is if vaccines cause autism. There are two theories that link autism and vaccines. The first suggests that the MMR (Mumps-Measles-Rubella) vaccine may cause intestinal problems leading to the development of autism. The second theory suggests that a mercury-based perservative called thimerosal, used in some vaccines, could be connected to autism. Nearly all of the leading health organizations including the CDC and the NIH say that there is no relationship between vaccines and autism. Yet, parents and smaller research groups are convinced otherwise.