Although the genetic basis of autism is now well established, a growing body of research also suggests that environmental factors may play a role in this serious developmental disorder affecting nearly one in 100 children.

Using a unique study design, a new study suggests that low birth weight is an important environmental factor contributing to the risk of autism spectrum disorder (ASD).

 “Our study of discordant twins — twin pairs in which only one twin was affected by ASD — found birth weight to be a very strong predictor of autism spectrum disorder,” said Northwestern University researcher Molly Losh. Losh, who teaches and conducts research in Northwestern’s School of Communication, is lead author of the study that will be published in the journal “Psychological Medicine” and is now available online.  

Prior twin studies have shown that when one identical twin had ASD, the other twin was much more likely to have ASD than not. “Because identical twins share virtually 100 percent of their genes, this is strong evidence for the role of genetics in autism,” said Losh. “Yet it is not 100 percent the case that ASD affects both identical twins in a twin pair.”    

“That only one twin is affected by ASD in some identical twin pairs suggests that environmental factors may play a role either independently or in interaction with autism risk genes,” she added.

“And because autism is a developmental disorder impacting brain development early on, it suggests that prenatal and perinatal environmental factors may be of particular importance.“

Continue reading this article by Wendy Leopold at Northwester.edu for more information on autism.