Sex differences in pervasive developmental disorders.

Assessed differences in sex ratio, severity of associated mental retardation, and various metrics of severity of autism in autistic, PDD-NOS, and developmentally disordered (non-PDD) cases. Males with autism were more frequent than females, particular at higher IQ levels. The three clinical groups differed, in expected ways, in the various measures of severity of autism with the PDD-NOS cases being intermediate between the strictly diagnosed autistic group and the non-PDD developmental disordered group. Sex differences were primarily confined to IQ; sex differences in other metrics of severity of autism were not prominent. Implications for future research are discussed.