Medical cannabis laws were associated with 43% lower odds of opioid misuse among past-year cannabis users, but showed no overall population-level effect on opioid outcomes.
Policymakers evaluating cannabis-opioid substitution claims and clinicians considering cannabis for pain patients on opioids.
43% lower opioid misuse odds among cannabis users in MCL states
What the researchers found
Overall, neither medical nor recreational cannabis laws were associated with changes in opioid misuse or use disorder at the population level. However, among individuals reporting past-year cannabis use, medical cannabis laws were associated with 43% lower odds of opioid misuse (AOR 0.57, FDR p = 0.07) compared to states without cannabis laws. Recreational laws showed no additional effect beyond medical legalization.
Why it matters
This study resolves a debate by showing that the opioid-cannabis substitution effect may be real but limited to people who are already using cannabis. The lack of a population-level effect explains why some studies find substitution while others do not.
The numbers in context
NSDUH 2015-2019. Overall: no significant association between cannabis laws and opioid outcomes. Among past-year cannabis users in MCL states: AOR 0.57 (95% CI: 0.38-0.85) for opioid misuse. FDR-corrected p = 0.07. RCL: no additional effect.
How the study worked
Analysis of NSDUH data from 2015-2019 using logistic regression with year and state fixed effects, individual covariates, and opioid-related state policies. Stratified analyses restricted to individuals reporting lifetime cannabis use prior to law adoption to reduce collider bias. False discovery rate corrections and e-values assessed robustness.
What this study cannot tell us
NSDUH is self-reported and cross-sectional within waves. The FDR-corrected p-value of 0.07 is marginally significant. Restricting to past-year cannabis users introduces selection effects. Cannabis use prior to law adoption does not guarantee continued use after.
How to read the evidence
National survey data with state and year fixed effects and sensitivity analyses. Strong methodology, but marginally significant primary finding (FDR p = 0.07).
When this study was published
Published in 2025 with NSDUH data from 2015-2019.
The bigger picture
The finding that cannabis substitution for opioids only works among existing cannabis users has important policy implications. Legalizing cannabis may not reduce opioid problems at the population level, but it may benefit a subgroup already self-medicating with cannabis.
Questions still open
- Could medical cannabis programs be designed to more effectively reach opioid users? Why does recreational legalization not add further opioid reduction beyond medical access?
Common questions
Does cannabis legalization reduce the opioid crisis?
Why only medical and not recreational laws?
Read the original research
The relationship of medical and recreational cannabis laws with opioid misuse and opioid use disorder in the USA: Does it depend on prior history of cannabis use?
The International journal on drug policy, 136, 104687
Citation
Martins, Silvia S; Bruzelius, Emilie; Mauro, Christine M; Santaella-Tenorio, Julian; Boustead, Anne E; Wheeler-Martin, Katherine; Samples, Hillary; Hasin, Deborah S; Fink, David S; Rudolph, Kara E; Crystal, Stephen; Davis, Corey S; Cerdá, Magdalena. (2025). The relationship of medical and recreational cannabis laws with opioid misuse and opioid use disorder in the USA: Does it depend on prior history of cannabis use?. The International journal on drug policy, 136, 104687. https://doi.org/10.1016/j.drugpo.2024.104687