Aims: Among patients with substance dependence and comorbid major depressive disorder (MDD) receiving treatment in a controlled trial, we examined if group differences in depression were mediated by 12-Step involvement, and if the effects of 12-Step involvement on future alcohol and drug use were mediated by reductions in depression.
Design: Controlled trial of Twelve-Step facilitation (TSF) and integrated cognitive-behavioral therapy (ICBT), delivered in out-patient groups for 6 months with adjunct pharmacotherapy.
Setting: Out-patient dual diagnosis clinic in Veteran's Affairs Healthcare Center.
Participants: Veterans (n = 209) diagnosed with alcohol, stimulant or marijuana dependence and substance-independent MDD.
Measurements: Twelve-Step attendance and affiliation, depression severity, percentage of days drinking and percentage of days using drugs assessed at baseline and months 3, 6 and 9.
Findings: In multi-level analyses greater 12-Step meeting attendance predicted lower depression and mediated the superior depression outcomes of the TSF group, explaining 24.3% of the group difference in depression. Independent of treatment group, lower depression severity predicted lower future alcohol use and mediated the effects of 12-Step meetings, explaining 15.7% of their effects on future drinking. Controlled, lagged models indicated these effects were not confounded by current substance use, suggesting that depression had unique associations with 12-Step meeting attendance and future drinking.
Conclusions: For patients with substance dependence and major depressive disorder, attendance at 12-Step meetings is associated with mental health benefits that extend beyond substance use, and reduced depression could be a key mechanism whereby 12-Step meetings reduce future drinking in this population.
Trial registration: ClinicalTrials.gov NCT00018655 NCT00108407.
© 2012 The Authors. Addiction © 2012 Society for the Study of Addiction.