ABSTRACT
INTRODUCTION: Prior systematic and meta-analytic reviews observed mixed evidence for the efficacy of cannabis brief interventions (BIs). Inconsistent support for cannabis BIs may be the result of intersecting methodological factors, including intervention structure and content, participant eligibility criteria, and outcome assessment measures. The current systematic review of cannabis BI studies narratively synthesizes these data to guide intervention development decision-making in future cannabis BI studies (PROSPERO CRD42022285990). METHODS: We searched PubMed/MEDLINE, PsycINFO, and CINAHL databases in January 2022 and again in June 2023 to capture newly published studies. Studies were included if they were a randomized trial, enrolled adolescents (13-17) and/or young adults (18-30), specified cannabis use and/or problems inclusion criteria, and evaluated a cannabis BI (defined as ≤4 sessions). We extracted and synthesized data on intervention characteristics (e.g., components, length/duration, modality), cannabis inclusion criteria and recruitment setting, baseline cannabis use descriptives and treatment-seeking status, and outcome assessment measures to discern if/how they may intersect to determine intervention efficacy. The Cochrane Risk of Bias Tool 2 assessed study quality. RESULTS: Our search resulted in a final sample of 25 study records including 4094 participants. Recruitment setting seemed to provide an influential backdrop for how well inclusion criteria determined baseline cannabis use level, as well as for the type/length of the BI evaluated. Motivational interviewing (MI) and personalized feedback (PF) were the most frequently used BI components overall; however, some differences were observed in the proportion of BIs with reported intervention effects using MI vs. PF. Frequency of use days was the most commonly used outcome measure, although this may not be the most sensitive measure for assessing cannabis BI efficacy. CONCLUSIONS: Our systematic review indicates that cannabis BI studies require greater precision in their design, giving special attention to matching the content and structure of the BI to the needs of the target population and selecting outcomes commensurate to the goals of the BI and the target population to more accurately reflect the efficacy of the BI. However, consistent with prior reviews, all included studies demonstrated at least some concerns for risk of bias, and most were at high risk.
