Trial finds less marijuana use after added motivational therapy

Marijuana use among older adolescents, particularly African American women, is associated with adverse health outcomes and frequently co-occurs with alcohol use and sexual risk behaviors. Evidence-based interventions targeting alcohol and sexual risk rarely evaluate their impact on marijuana use, leaving a critical gap for this underserved population. The present study examined whether the benefits of Horizons + GMET, an intervention combining an evidence-based STI/HIV risk-reduction program (Horizons) with Group Motivational Enhancement Therapy (GMET), extend to marijuana use frequency and problem severity. In this secondary analysis of a randomized controlled trial, 560 African American women aged 18-24, recruited from community venues in Atlanta, Georgia, were randomly assigned to Horizons + GMET, Horizons-only, or an enhanced standard-of-care control condition, with assessments every 3 months through 12 months. Zero-inflated negative binomial models with multiple imputation estimated intervention effects on past-month days of marijuana use and marijuana-related problem severity. Over 12 months, relative to the Horizons-only condition, Horizons + GMET participants reported 22% fewer days of marijuana use in the past month and 39% lower marijuana-related problem severity. Reductions in marijuana use were not accompanied by compensatory increases in alcohol misuse, suggesting no behavioral substitution. Findings indicate that motivational and behavioral self-regulation skills developed in the context of alcohol and sexual risk reduction may generalize to marijuana use, even when not an explicit intervention target. The study highlights the potential of integrated, community-delivered interventions to address co-occurring health risks among young African American women. Young African American women face compounding vulnerabilities including trauma exposure, STI burden, and co-occurring substance use. This study demonstrates that an integrated, motivational intervention can simultaneously reduce marijuana use frequency and problem severity without risk compensation, offering an efficient and scalable model for addressing multiple co-occurring health risks in an underserved community-based population.