Abstract
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 expands 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 effects. Findings 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]), consumption level (g = 0.01, 95% CI [− 0.07, 0.09]), or severity (g = 0.13, 95% CI [− 0.07, 0.33]). Similarly, there was no evidence of effects on long-term cannabis use (OR = 1.19, 95% CI [0.73, 1.86]) or consumption level (g = 0.04, 95% CI [− 0.05, 0.12]). Although the primary analyses did not provide evidence of effect moderation, sensitivity tests revealed BDIs delivered in emergency departments evidenced small but significant reductions in long-term cannabis consumption levels. While these findings do not provide support for the overall effectiveness of BDIs on cannabis consumption or severity in general medical settings, they offer suggestive 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. Given the importance of preventing adverse health outcomes and consequences of cannabis use, more research is needed to improve and evaluate BDI outcomes. Further, developing and testing alternative prevention and intervention approaches are essential to comprehensively address cannabis use.