The state of the evidence on the association between state cannabis laws and opioid-related outcomes: A review.

Abstract

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. Twenty-one U.S. based studies published between 2014-2021 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. 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.