The University of California at San Francisco and Stanford University have just released a report that the environmental factors account for 62% for the risk of the autism while only genetics accounts for 38%. Looking at 192 pairs of twins led them to this conclusion which revises previous knowledge that genetics played 90% risk for autism. They're also seeing that antidepressants used by mothers while pregnant may increase the risk of autism in their children.
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/07/04/MNG01K5FK7.DTL
