Methods: We conducted a systematic review and meta-analysis to synthesize evidence from primary studies using experimental or quasi-experimental designs to evaluate the effects of a BAI on alcohol outcomes among youth. The literature search identified 190 eligible trials, which were primarily located in the United States (76%) and used randomized controlled trial designs (89%). Most (93%) of the BAIs were delivered in school-based settings and on average, delivered in 1-2 sessions. We extracted over 1,500 standardized mean difference effect sizes indexing post-intervention differences in mean alcohol consumption. Multivariate mixed-effect meta-regression models with robust standard errors were used to examine average posttest effects and to explore variability in effects across settings, contexts, and intervention characteristics.
Results: BAIs were associated with significant reductions in alcohol consumption among adolescents (ave g = 0.25, 95% CI [0.13, 0.37]) and young adults (ave g = 0.15, 95% CI [0.12, 0.18]); these effects were equivalent to a difference in 1-4 drinking days per month. BAIs using motivational interviewing approaches were the most effective. Further, BAIs were more effective for adolescents when the interventions included decisional balance or goal-setting exercises to motivate intentions for behavior change.
Conclusions: BAIs can be effective at reducing alcohol consumption among youth, but there is considerable variability in effectiveness. This meta-analysis has helped advance the field by identifying some of the key ingredients that may optimize response to BAIs. Nonetheless, this meta-analysis was limited by a reliance on aggregate trial data. We will therefore discuss two primary limitations: (1) inability to fully explore participant characteristics that modify intervention effectiveness and (2) difficulties estimating effect size parameters appropriate for overdispersed count outcomes. This discussion will highlight the need for innovative individual participant data meta-analysis approaches, which can help advance a precision medicine lens regarding for whom and under what conditions BAIs are more effective.