Is autistic disorder an inherited disorder?
• Some types of autistic disorder are inherited, either alone or as part of a genetic syndrome, while other types of autistic disorder seem to be caused by environmental factors. Autistic disorder that runs in families is due in large part to genetic factors. In some instances, autistic disorder is a feature of a known genetic syndrome. However, much more frequently no specific cause is found (this is called idiopathic autistic disorder, meaning autistic disorder of unknown cause). There is a great deal of evidence that autistic disorder with an unknown cause actually is caused by changes or “mutations” in genes. Twin studies show much higher concordance rates for autism among identical twins than among non-identical (fraternal) twins. Concordance refers to the likelihood that if one twin has a diagnosis of autism, the second twin will also have a diagnosis of autism. Family studies have found that relatives of a person with autistic disorder have a higher chance of having autistic dis
