Hans Asperger described common symptoms among his patients' family members, especially fathers, and research supports this observation and suggests a genetic contribution to Aspergers. Although no specific gene has yet been identified, multiple factors are believed to play a role in the expression of autism, given the phenotypic variability seen in this group of children.
Evidence for a genetic link is the tendency for Aspergers to run in families and an observed higher incidence of family members who have behavioral symptoms similar to Aspergers, but in a more limited form (e.g., slight difficulties with social interaction, language, or reading).
Most research suggests that all autism spectrum disorders have shared genetic mechanisms, but Aspergers may have a stronger genetic component than autism.
There is probably a common group of genes where particular alleles render an individual vulnerable to developing Aspergers; if this is the case, the particular combination of alleles would determine the severity and symptoms for each individual with Aspergers.
A few autism spectrum disorder cases have been linked to exposure to teratogens (agents that cause birth defects) during the first eight weeks from conception. Although this does not exclude the possibility that autism spectrum disorders can be initiated or affected later, it is strong evidence that it arises very early in development.
Many environmental factors have been hypothesized to act after birth, but none has been confirmed by scientific investigation.
Causes of Autism—
Autism and autism spectrum disorders are complex neurodevelopmental disorders Many causes of autism 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.
The Parenting Aspergers Resource Guide: A Complete Resource Guide For Parents Who Have Children Diagnosed With Aspergers Syndrome.