Age of onset and course of major depressive disorder: associations with psychosocial functioning outcomes in adulthood

Background. Major depressive disorder (MDD) that onsets by adolescence is associated with various deficits in psychosocial functioning. However, adolescent-onset MDD often follows a recurrent course that may drive its associated impairment. Method. To tease apart these two clinical features, we examined the relative associations of age of onset (adolescent versus adult) and course (recurrent versus single episodes) of MDD with a broad range of psychosocial functioning outcomes assessed in early adulthood. Participants comprised a large, population-based sample of male and female twins from the Minnesota Twin Family Study (MTFS; n=1252) assessed prospectively from ages 17 to 29 years. Results. A recurrent course of MDD predicted impairment in several psychosocial domains in adulthood, regardless of whether the onset was in adolescence or adulthood. By contrast, adolescent-onset MDD showed less evidence of impairment in adulthood after accounting for recurrence. Individuals with both an adolescent onset and recurrent episodes of MDD represented a particularly severe group with pervasive psychosocial impairment in adulthood. Conclusions. The negative implications of adolescent-onset MDD for psychosocial functioning in adulthood seem to be due primarily to its frequently recurrent course, rather than its early onset, per se. The results highlight the importance of considering both age of onset and course for understanding MDD and its implications for functioning, and also in guiding targeted intervention efforts.