Brief interventions for cannabis use in emerging adults: A systematic review, meta-analysis, and evidence map

Purpose: This systematic review summarizes and critically appraises the existing literature on brief interventions (Bls) for cannabis use among emerging adults. Methods: Eligible Bls were operationalized as 1-2 sessions focused exclusively on cannabis use for samples with mean ages between 15 and 30. Outcomes related to cannabis use, other substance use, mental health, help-seeking, or functional status were included. Two independent reviewers screened a total of 3638 records, identifying 244 studies for full-text screening. In total, 32 BIs in 26 primary studies with 6318 participants were included. Results: Participants were typically not seeking treatment and using cannabis at least once a month. Most interventions were motivational, single sessions, and delivered in person. Few discussed concurrent psychiatric conditions. Pooling results at 1-3 months post-intervention, Bls compared to passive control slightly reduced symptoms of cannabis use disorder (SMD 0.14 [95% CI 0.26 to 0.01]) and increased the odds of abstinence (OR 1.73 [95% CI 1.13-2.66]). Other outcome results often favored BIs but were not significant. Results of studies comparing types of BIs (k = 8) or Bls to longer interventions (k = 1) are discussed narratively. Quality assessment suggested low to very low-quality evidence. Conclusions: This review indicates that BIs targeting non-treatment seeking emerging adults result in significant reductions in symptoms of cannabis use disorder and an increased likelihood of cannabis abstinence, however evidence is of low quality.