Are the mentally retarded and learning disordered overrepresented among sex offenders and paraphilics?

A sample of 2,286 male sex offenders and paraphilics and 241 nonsex offenders was evaluated for the prevalence of mental retardation and learning disorders, using the full Wechsler IQ scales. The sex offenders were generally of average intelligence, and the mentally retarded were not overrepresented among them, but the learning disordered were. There were no differences among sex offenders and controls in overall IQ or in the percentage of mentally retarded or learning-disordered cases, suggesting that the learning difficulties are not peculiar to sex offenders. There was a bias in referral source, with more mentally retarded, borderline-retarded, and/or learning-disordered cases being referred by the Children's Aid Society, prisons, and the Crown, suggesting that referral source may play a significant role in evaluating intelligence and mental retardation among sex offenders; but the overrepresentation of learning disorders among criminals appears to be a significant phenomenon, regardless of referral source.