Major depression and conduct disorder in a twin sample: Gender, functioning, and risk for future psychopathology

Objective: Major depression (MDD) and conduct disorder (CD) co-occur in adolescents at rates higher than would be expected by chance. This study described the functioning of adolescents with histories of these disorders and examined whether these patterns of association differed by gender. Method: Subjects with a lifetime DSM-III-R diagnosis of MDD and/or CD were selected from a sample of 17-year-old twins; control subjects had no history of either disorder. The domains of school success, substance dependence, peer relationships, and age of first sexual intercourse were examined. Results: Overall, each disorder separately and especially both disorders together related to increased maladjustment in the domains of school success and substance dependence. For school behavior problems, nicotine dependence, and drug dependence, the combination of MDD and CD related to particularly problematic functioning. Results were similar for males and females. Longitudinal data indicated that the occurrence of these disorders by late adolescence was predictive of subsequent depression and antisocial behavior in early adulthood. Conclusions: The combination of CD and MDD relates to more serious maladjustment, especially relating to school success and substance dependence, than would be expected given the adjustment associated with each disorder alone.