The State of the Evidence on the Association Between State Cannabis Laws and Opioid-Related Outcomes: a Review

Purpose of Review This review summarizes studies examining impacts of medical and recreational cannabis laws on opioid prescribing, opioid use, opioid use disorder, opioid-related service utilization, and opioid-involved mortality. We also discuss research challenges and recommendations for future work. Recent Findings Twenty-one US-based studies published between 2014 and 2021 that assessed state cannabis laws’ association with opioid-related outcomes were reviewed. Study results were largely inconclusive. We identified six challenges of existing work: (1) inability to directly measure cannabis/opioid substitution; (2) use of general population samples and lack of individual-level longitudinal studies; (3) challenges disentangling effects of cannabis laws from other state laws; (4) methodological challenges with staggered policy implementation; (5) limited consideration of cannabis law provisions; (6) lack of triangulation across data sources. Summary While existing research suggests the potential for cannabis laws to reduce high-risk opioid prescribing and other opioid-related adverse outcomes, studies should be interpreted in light of limitations.