The intellectually disabled offender and the influence of a major psychiatric disorder on violent crime

It was hypothesized that there is a higher incidence of violent arrests among intellectually disabled offenders with a major psychiatric disorder than among those without a major psychiatric disorder. The historical records of approximately 200 intellectually disabled individuals who had been arrested for a crime were retrospectively reviewed. One group (n = 95) had individuals with a universally accepted intellectual disability, a major psychiatric diagnosis and an arrest for a crime and the comparison group (n = 98) did not have a major psychiatric disorder. The frequency of crime for intellectually disabled offenders with a psychiatric diagnosis was compared to the frequency of violent and nonviolent crime offenders without a psychiatric diagnosis by using odds ratios. Chi-square tests and Fisher's exact tests were used to determine whether the differences between the two groups were significant. The results indicated that the rate of violent offenses was 1.6 times greater among the intellectually disabled offenders with a psychiatric disorder than among the intellectually disabled offenders without a psychiatric disorder.