Many causes of autism have been proposed, but understanding of the theory of causation of autism and the other autism spectrum disorders is incomplete. It was once thought that heritability contributes about 90% of the risk of a child developing autism, but environmental factors have been underestimated, and genetics overestimated, for their roles in autism-spectrum disorders. The heritability of autism is complex and it is typically unclear which genes are responsible. In rare cases, autism is strongly associated with agents that cause birth defects. Many other causes have been proposed, such as childhood immunizations, but numerous clinical studies have shown no scientific evidence supporting any link between vaccinations and autism.
Read more about Causes Of Autism: Autism and Related Disorders, Genetics, Prenatal Environment, Perinatal Environment, Postnatal Environment, Social Construct, Evolutionary Psychology