Patients with dual diagnoses or substance use disorders only: 12-step group participation and 1-year outcomes.

We compared outpatients (regional facility) with substance use and psychiatric (N = 199) or only substance use (N = 146) disorders on baseline and one-year symptoms (93% follow-up), and treatment and 12-step group participation over the year (2005). We examined whether diagnostic status moderated associations between participation and outcomes (Addiction Severity Index) with regressions. At follow-up, dual diagnosis patients had more severe symptoms, despite comparable treatment. The groups were comparable on 12-step participation, which was associated with better outcomes. However, associations of participation with better outcomes were weaker for dual diagnosis patients. Study (VA HSR&D-funded) implications and limitations are noted and research suggested.