Autism and autism spectrum disorders are complex neurodevelopmental disorders. Many<unk>  have been proposed, but its theory of causation is still incomplete. Heritability contributes about 90% of the risk of a child developing autism, but the genetics of autism are complex and typically it is 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 exposure of children to vaccines; these proposals are controversial and the vaccine hypotheses have no convincing scientific evidence.
Causes of autism
Autism causes
Autism pathophysiology
Conditions comorbid to autism spectrum disorders
Mental retardation pathophysiology
Schizophrenia causes
Mental retardation causes
Fragile X syndrome risk factors