Assessed differences in sex ratio, severity of associated mental retar
dation, and various metrics of severity of autism in autistic, PDD-NOS
, and developmentally disordered (non-PDD) cases. Males with autism we
re more frequent than females, particular at higher IQ levels. The thr
ee clinical groups differed, in expected ways, in the various measures
of severity of autism with the PDD-NOS cases being intermediate betwe
en 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.