7.5.2011 11:40 AM

Study: Environment, More than Genetics, Triggers Autism

A new large study of twins and autism spectrum disorder finds that the environment in which a child develops may be more important than genetics.

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Photo: Istock

By Dan Shapley

A new study, which the National Institutes of Health calls "the largest and most rigorous twin study of its kind to date" finds that the environment has more to do with autism than previously thought, and may have more to do with the disease than genetics.

The findings turn conventional wisdom on its head, stating that environmental factors account for 55% of autism and 58% of autism spectrum disorder cases. That compares to 37% and 38% of cases attributable to genetics, according to the new analysis. Previous studies have found genetics responsible for as much as 90% of cases.

The study relied on a statistical analysis of twins diagnosed with autism, which is characterized by social and cognitive abnormalities, or one of the autism spectrum disorders, including Asperger syndrome.

The authors of the study acknowledge that the findings may be prone to some limitations, and their findings were met with mixed reactions from other scientists in the field. The Los Angeles Times quoted several skeptics and labeled the study "controversial", while other experts greeted it with a call for more research into potential environmental triggers of autism.

The study did not identify specific environmental factors that might trigger autism, but noted that they may include the age of the parents, low birth weight, multiple births and maternal infections during pregnancy. Other researchers have been searching for possible triggers of autism among chemicals to which mothers and young children are exposed.

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