Autism Q & A: What is the role of environment?

By Daniel B. Kessler, M.D.

What about the environmental causes of autism? Other than”What is autism?” there is no more controversial topic.

In particular there is the ongoing controversy surrounding the role of vaccines (particularly the MMR vaccine) and thimerisol, a mercury-based preservative that had been in many vaccines and may continue to be in some flu vaccines. Both have been blamed as causing autism. Though there is absolutely no scientific support for that position, debating the evidence is not appropriate in this brief forum.

If we stopped immunizations today there would be no decrease in the numbers of children diagnosed with autism (there was no decrease when thimerisol was removed from most vaccines, and in studies that compared the rate of autism in children who received immunizations and those who did not there were no differences) but a lot more children and adults would become sick and die from preventable illnesses. This is the critical public health role of immunizations, not to mention the degree of suffering and death that have been eliminated by their widespread use.

There is today little question that the environment plays a role in autism. Potential environmental factors range from the chemicals in food and cosmetics to parental age, maternal infections, stress and reproductive technologies.

A recent study suggests environmental factors play a more important role than previously indicated. In addition to having the right combination of genes, exposure to certain environmental factors might be necessary for autism to develop in certain individuals. The interaction of the two is an important target for future research. By studying genetic factors and determining their underlying mechanisms we may be better able to pinpoint environmental factors that contribute to autism.

What is challenging is identifying the potential environmental factors. Potential environmental factors range from the chemicals in food and cosmetics to parental age, maternal infections, stress and reproductive technologies. Some studies have focused on prenatal environmental factors such as agents that cause birth defects. Thalidomide (a sedative) and valproate (a seizure medicine) are known to increase the occurrence of autism when an exposure comes in the first trimester of pregnancy. All known such agents (teratogens) related to the risk of autism appear to act during the first eight weeks from conception, and though this does not exclude the possibility that autism can be initiated or affected later, it is strong evidence that autism arises very early in development.

The numbers of new chemicals introduced into the environment each year is alarming and growing. Of the 80,000 chemicals registered in the U.S., the EPA has required safety testing on only 200.  Are we testing them on our kids?

Next: Where to get help.

Daniel B. Kessler, M.D., is a developmental and behavioral pediatrician and medical director of the Children’s Developmental Center at Easter Seals Southwest Human Development. His private practice, where he provides evaluation and treatment for children and adolescents, is located at Southwest Human Development.

The views he expresses in this series are based on his training, his reading of the literature and his more than 30 years of experience taking care of hundreds of kids on the autism spectrum. The series begins here.

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