Comorbid depression and substance use disorder: longitudinal associations between symptoms in a controlled trial.

This study examined the longitudinal association between substance use and depressive symptoms in veterans receiving outpatient treatment for comorbid substance use disorder and major depression. Veterans (N = 237, mean age = 48.2 years, 90% male, 70% Caucasian) received either 6 months of group integrated cognitive-behavioral therapy or twelve-step facilitation. Hamilton Depression Rating Scale scores and percent days using any substance were assessed every 3 months up to 1 year posttreatment. Greater substance use predicted time-varying elevations in depression above individual patterns of change in depression. Moreover, change in depressive symptoms was associated with change in both the likelihood of any substance use and the frequency of use during the treatment and follow-up periods. Changes in these symptoms appear to be linked, such that individuals with greater reductions in substance use have greater reductions in depressive symptoms (and vice versa).