An important study released this week in the Journal of the American Medical Association indicates that environmental factors play a critical role in the development of autism spectrum disorders.
While the role of genetics has long been recognized as a causal factor in ASD, the role of environmental triggers has been less widely discussed.
This study shows that environmental factors are just as important as genes in the development of ASD, with heritability of autism at 50% and the other 50% explained by environmental factors. More specifically, they discovered that “non-shared environments” (those factors that are unique to the individual and not to the family as a whole) are critical. The authors indicate they were surprised to find that environment plays such a large role.
This research confirms what many families and professionals in the autism community have been saying for a long time:
There are environmental factors that need to be more thoroughly investigated in order to understand why the number of people with autism continues to rise. With the most recent CDC statistics showing that 1 in every 68 children in the United States has an autism spectrum disorder, the need to understand the role that environmental factors play in the development of ASD has never been greater. As the authors of this study stated, “Recent research efforts have tended to focus on genes, but it’s now clear that we need much more research to focus on identifying what these environmental factors are.”
Another important result of this study is the data showing that children with a sibling on the autism spectrum are 10 times more likely to develop autism than the general population. The likelihood is 3 times greater if the child has a half-sibling with autism, and 2 times greater if the child has a cousin with autism. This is very important information for families and professionals who respond to parent questions on this topic.
Sven Sandin, Paul Lichtenstein, Ralf Kuja-Halkola, Henrik Larsson, Christina M. Hultman, Abraham Reichenberg. The Familial Risk of Autism. JAMA, 2014; 311 (17): 1770 DOI: 10.1001/jama.2014.4144