JAMA: Autism - Familial Risk

"The Familial Risk of Autism"
http://jama.jamanetwork.com/article.aspx?articleid=1866100
"Conclusions and Relevance  Among children born in Sweden, the individual risk of ASD and autistic disorder increased with increasing genetic relatedness. Heritability of ASD and autistic disorder were estimated to be approximately 50%. These findings may inform the counseling of families with affected children."