In Autism Spectrum Disorders, Environment Matters As Much as Genes

A large-scale study examining how ASDs run in families yields results that surprise researchers.
ADHD News Feed | posted by Wayne Kalyn
ADHD and Autism in the Classroom © istockphoto/ktaylorg

Environmental factors are more important than previously thought in understanding the causes of autism spectrum disorder, according to the largest study to date to look at how the disorder runs in families.

The study also reinforces the findings of other research that shows that genetics play a strong role in the likelihood of developing the disorder. Children with a brother or sister with autism are 10 times more likely to develop autism; 3 times more likely if they have a half-brother or sister; and 2 times more likely if they have a cousin with autism.

The researchers split environmental factors into “shared environments” shared by family members (such as socio-economic status) and “non-shared environments,” which are unique to the individual (such as birth complications, maternal infections, or medication during the pre- and perinatal phase). In this study, “non-shared environments” were the major source of environmental risk.

Avi Reichenberg, Ph.D., a professor of psychiatry and preventive medicine at the Icahn School of Medicine at Mount Sinai, along with a research team from the Karolinska Institutet in Stockholm, Sweden, and King’s College in London conducted the study, which was published in the Journal of the American Medical Association several weeks ago.

“We were surprised by our findings as we did not expect the importance of environmental factors to be so strong. Recent research efforts have tended to focus on genes, but it’s now clear that we need much more research on identifying what these environmental factors are,” says Dr. Reichenberg.

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