Peer-Enhanced Motivational Interviewing for Emerging Adults Misusing Substances: A Randomized Study

Purpose: Few studies include peers in brief motivational interventions (BMIs) for substance misuse. This study tested a peer-enhanced BMI, where friends in emerging adults’ (EAs) social networks attended interventions. Method: Dyads were randomized to Peer-Enhanced Motivational Interviewing (PMI) or waitlist control (WC) conditions (NCT03264872). Seventy-four dyads ( n = 188) enrolled, completing surveys at baseline and then biweekly for 12 weeks. Primary outcomes included cannabis and alcohol problem indices. Supplemental measures were peer supportive behaviors, days of binge drinking, and alcohol-related problems. Linear, quadratic, and piecewise growth models tested differences in trends through 12 weeks. Results: For target clients, most results favored the PMI group with significant differences and moderate effects at select time points. However, these no significant between group differences in trends were observed between conditions through 12 weeks. Peer supportive behaviors increased significantly at 2 weeks among peers receiving PMI, but this effect faded through 12 weeks. Discussion: PMI is a promising dyadic-based treatment for EA substance misuse that should be studied further with larger samples.