Environmental influences may play a more prominent role in the development of autism than previously thought, according to a study funded by National Institute of Mental Health.
The study (Hallmayer J et al. Arch Gen Psychiatry. 10.1001/archgenpsychiatry.2011.76 [published online ahead of print July 4, 2011]) involved 192 California twin pairs born between 1987 and 2004 in which at least 1 twin had a diagnosis of an autism spectrum disorder. The researchers found that shared environmental factors accounted for 55% of the risk of developing autism and 58% of the risk of developing autism spectrum disorders, while genetic factors accounted for 37% and 38% of such risks, respectively. Previous studies had suggested that as many as 90% of cases of autism spectrum disorders may be related to genetic factors.
Kuehn BM. Environment and Autism. JAMA. 2011;306(8):815. doi:10.1001/jama.2011.1200