A Preliminary Test of a Brief Intervention to Lessen Young Adults’ Cannabis Use: Episode-Level Smartphone Data Highlights the Role of Protective Behavioral Strategies and Exercise

Brief interventions are increasingly being used to help young adults to moderate their cannabis use. We conducted a randomized clinical trial of a brief (4 weekly sessions), in-person intervention that included a smartphone application that reinforced the use of protective behavioral strategies (PBSs) to lessen cannabis use. Young adults (N = 37; 24 men) who regularly used cannabis were randomized to 2 intervention conditions rooted in cognitive–behavioral therapy (CBT) and motivational enhancement therapy (MET). Along with learning CBT + MET strategies, participants in 1 of the conditions were instructed to engage in exercise. All participants used smartphone-based ecological momentary assessment to provide episode-level reports about use of cannabis and PBSs. Two multilevel structural equation models were run to test the study hypotheses that (a) cannabis use would be reduced over the course of the 6-month study, (b) reductions would be moderated by intervention condition, and (c) episode-level PBS use would predict episode-level cannabis use. Participants reduced their cannabis use by approximately 1 half of a standard joint per time point. The MET + CBT + Exercise condition reduced cannabis use to a greater degree than did the MET + CBT condition. With episode-level PBS use in the model, reductions in cannabis use were independent of intervention condition. Our findings suggest that young adults will engage with a smartphone app that serves as a component of an in-person intervention to moderate their cannabis use. Intervention content that promotes the use of PBSs and exercise facilitates reductions in cannabis use.