Brief Drug Interventions Delivered in General Medical Settings: A Systematic Review and Meta-Analysis of Cannabis Use Outcomes

There is consistent evidence that brief interventions can be effective in preventing and reducing alcohol use, but support for their effects on illicit drug use is more limited. This meta-analysis builds upon prior research by testing whether brief drug interventions (BDIs) delivered in general medical settings reduce cannabis consumption and severity across post-intervention follow-up periods and explores potential heterogeneity in these intervention effects. Effect sizes from 17 randomized controlled trials were synthesized to compare short and long-term cannabis use outcomes between intervention and control groups. Mixed effects meta-regression models were estimated to examine variability in effects across four intervention characteristics: booster session delivery, delivery setting, intervention target, and target population. Sensitivity tests were also conducted for both main effects and moderation analyses. There was no evidence that BDIs yielded significant short-term reductions in cannabis use (OR = 1.20, 95% CI [0.90, 1.62]), frequency (g = 0.01, 95% CI [-0.07, 0.09]), or severity (g = 0.13, 95% CI [-0.07, 0.33]). Similarly, no evidence of long-term cannabis use (OR = 1.19, 95% CI [0.73, 1.86]) or frequency (g = 0.04, 95% CI [-0.05, 0.12]) were observed. Although the primary moderation analyses did not provide evidence of variation in effects, sensitivity tests revealed that BDIs delivered in emergency departments evidenced small but significant reductions in long-term frequency of cannabis use. Although these findings do not lend meaningful support for the overall effectiveness BDIs on cannabis consumption or severity when delivered in general medical settings, they do indeed provide secondary evidence that BDIs may perform more favorably when delivered in emergency departments. Thus, high-quality trials evaluating the effects of BDIs in emergency departments are needed. Further, given the importance of preventing adverse health outcomes and consequences of cannabis use, further research is clearly needed to improve and evaluate BDI outcomes as well as develop and test alternative prevention and intervention approaches to comprehensively address cannabis use.