Genetic Risk Factors | Neurobiological Factors | Psychological Theories | Parental Age
Autism is the most highly heritable of all mental disorders,
exceeding that of schizophrenia or bipolar disorder. Twin and family
studies have convincingly demonstrated that genetic factors play
a role in disorders throughout the autism spectrum (for a review, see Lauritsen and Ewald 2001). Recent studies have shown that the concordance
rates in monozygotic twins is between 60% and 90%.
In those instances where the twins were discordant for autism, the
nonautistic twin often had impairments in communication and social
interaction as well as stereotypic behaviors, though not at a sufficient
level to merit a diagnosis. The likelihood that the parents of a
child with autism will have another child with autism has been estimated
at 3%–5%. This is likely to be an underestimation,
since parents may elect to have no more children after the autistic
child is diagnosed.