Behavioural deviance in children with early treated phenylketonuria.

A sample of 99 early treated phenylketonuric children showed higher levels of behavioural deviance than 197 matched controls. For boys this excess of behavioural deviance persisted when IQ was taken into account. For phenylketonuric girls however it was restricted to those with IQs less than 70. The type of behavioural deviance shown by the boys over the whole IQ range was predominantly neurotic. The levels of behavioural deviance found in phenylketonuric children were among the highest that have been reported for children with various handicapping conditions.