Correlation of family history with specific autistic subgroups: Asperger's syndrome and bipolar affective disease.

The etiology of infantile autism is not known. To assess the possible role of familial psychopathology, we investigated a group of autistic subjects subgrouped by level of language function. Family histories were obtained by the family history method. Neurological status was assessed by neurological diagnostic examination and prenatal and perinatal history. The results showed a high incidence of Asperger's syndrome in family members of high-functioning autistic subjects only. The rate of bipolar affective disorder in family members was 4.2%, higher than in the general population; it was significantly higher in families with Asperger's syndrome, suggesting an etiological link between Asperger's syndrome and manic depression. Positive neurological findings were concentrated in the low-functioning subgroup. These findings imply different etiologies for high- versus low-functioning autism, with high-functioning autism related to familial factors, especially Asperger's syndrome.