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).
Â â€śOur 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,â€ť said Northwestern University researcherÂ Molly Losh. Losh, who teaches and conducts research in Northwesternâ€™sÂ School of Communication, is lead author of the study that will be published in the journal â€śPsychological Medicineâ€ť and is now available online.Â Â
Prior twin studies have shown that when one identical twin had ASD, the other twin was much more likely to have ASD than not.Â â€śBecause identical twins share virtually 100 percent of their genes, this is strong evidence for the role of genetics in autism,â€ť said Losh. â€śYet it is not 100 percent the case that ASD affects both identical twins in a twin pair.â€ť Â Â Â
â€śThat 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,â€ť she added.
â€śAnd because autism is a developmental disorder impacting brain development early on, it suggests that prenatal and perinatal environmental factors may be of particular importance.â€ś