Autism

The causes of autism remain incompletely understood, although 40 percent to 60 percent of cases are believed to have a genetic component traced to multiple genes predisposing development of different aspects of autism. Concordance in monozygotic (identical) twins is around 95 percent; in dizygotic (fraternal) twins, around 9 percent; and in siblings, 3 percent. About 15 percent to 25 percent of siblings of individuals with autism have mild to severe language difficulties.