The main purpose of this project is to test whether Peer-Enhanced Motivational Interviewing (PMI) results in superior alcohol and marijuana use outcomes for emerging adults (EAs, ages 18-29) and their peers. Ninety peer dyads (total n = 180, ntarget client = 90, npeer = 90) are randomized to receive either Peer-Enhanced Motivational Interviewing (PMI) or Waitlist Control (WC).

This project randomized peer dyads, consisting of one EA (Emerging Adult; 18-29 years old) with a substance use problem (i.e. target client) and one peer, to one of two conditions. In the Peer-Enhanced Motivational Interviewing (PMI) condition, target clients and peers will receive separate one-hour sessions of Motivational Interviewing (MI) , an empirically-supported treatment that helps individuals work through ambivalence about making changes in substance use. MI is thought to work because it is a non-confrontational intervention where a therapist empathetically reviews substance use behaviors, listens empathetically, and reinforces any client statements indicating a desire to change. With the 'peer' of each PMI dyad, the therapist presents peers with data about the extent of the target client's substance use, builds the peer's motivation to help their friend, and teaches the peer communication skills they can use to influence the target client's substance use. In the WC condition, target clients and peers can receive PMI after the study follow-up period. Both target clients and their peers are followed for 12 weeks post-intervention.

The main purpose of this project is to test whether Peer-Enhanced Motivational Interviewing (PMI) results in superior alcohol and marijuana use outcomes for emerging adults (EAs, ages 18-29) and their peers. Ninety peer dyads (total n = 180, ntarget client = 90, npeer = 90) are randomized to receive either Peer-Enhanced Motivational Intervie (PMI) or Waitlist Control (WC).

Inclusion Criteria:

For the Target Client

• Score 5 or higher on the AUDIT-C measure and/or use alcohol or marijuana 13 days or more out of the past 90 days,
• Have a friend that they are willing to refer to the study to be their 'peer' (support) and that peer agrees to participate,
• Are able to complete baseline and follow-up assessments and have a valid email,
• Are willing to be video recorded, and
• Are fluent in English

For the Peer

• Have weekly contact with the participating Target Client who referred them,
• Are will to attend all study procedures (i.e. baseline assessment, intervention, follow up),
• Are willing to be video record,
• Are fluent in English

Exclusion Criteria:

For the Target Client

• Are current students in the lead Investigator's classes,
• Are seeking residential treatment at the time of the screening call,
• Are incarcerated or court-ordered to receive treatment at the time of the screening call,
• Use drugs besides marijuana or alcohol over 45 of the past 90 days.

For the Peer

• Are current students in the lead Investigator's classes,
• Are seeking residential treatment at the time of the screening call,
• Are incarcerated or court-ordered to receive treatment at the time of the screening call,
• Use drugs besides marijuana or alcohol over 45 of the past 90 days,
• Are romantic partners of the Target Client