Co-morbid psychiatric disorders among incarcerated ADHD populations: a meta-analysis

BACKGROUND: Rates of psychiatric disorders are highly prevalent among prison inmates, and recent evidence confirms over-representation of youths and adults with attention deficit hyperactivity disorder (ADHD). The risk for psychiatric co-morbidity may be greater among offenders with ADHD. We undertook a systematic review and meta-analysis of reported rates of co-existing psychiatric morbidity with ADHD in prison samples. METHOD: Studies published from 1980 to 2015 were identified using five bibliographic indexes, review articles and reference lists. Included studies had a defined ADHD group and provided additional prevalence on at least one of the following: conduct disorder, substance use disorder, mood disorder, anxiety disorder, or personality disorder. We performed meta-analytical estimates of the prevalence of each co-morbid disorder within ADHD, and estimated the risk for co-existing disorders among prisoners with ADHD by pooling odds ratios (OR) with 95% confidence intervals. RESULTS: Eighteen studies with data for 1615 with ADHD and 3128 without ADHD were included. The risk (OR) of all psychiatric morbidity is increased among adult inmates with ADHD. Associations in youths with ADHD were restricted to mood disorder (OR 1.89, 95% confidence interval 1.09–3.28). CONCLUSIONS: This study quantifies the extent of co-morbidity presented by offenders with ADHD, especially adults. The differences between risk estimates for youths and adults indicate an incremental effect in both frequency and severity for the development of further co-morbid pathology through adulthood. The findings have implications for clinical intervention and for criminal justice policy.