Medical Cannabis Laws May Reduce Opioid Misuse, but Only Among People Already Using Cannabis
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.
Quick Facts
What This Study 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.
Key Numbers
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 They Did This
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.
Why This Research 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 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.
What This Study Doesn't 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.
Questions This Raises
- ?Could medical cannabis programs be designed to more effectively reach opioid users?
- ?Why does recreational legalization not add further opioid reduction beyond medical access?
Trust & Context
- Key Stat:
- 43% lower opioid misuse odds among cannabis users in MCL states
- Evidence Grade:
- National survey data with state and year fixed effects and sensitivity analyses. Strong methodology, but marginally significant primary finding (FDR p = 0.07).
- Study Age:
- Published in 2025 with NSDUH data from 2015-2019.
- Original Title:
- 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?
- Published In:
- The International journal on drug policy, 136, 104687 (2025)
- Authors:
- Martins, Silvia S(20), Bruzelius, Emilie(4), Mauro, Christine M(5), 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
- Database ID:
- RTHC-07069
Evidence Hierarchy
Looks back at existing records to find patterns.
What do these levels mean? →Frequently Asked Questions
Does cannabis legalization reduce the opioid crisis?
Not at the population level, according to this study. The reduction in opioid misuse was only seen among people already using cannabis, suggesting substitution occurs individually but does not move the needle for overall opioid disorder rates.
Why only medical and not recreational laws?
Recreational laws did not show additional opioid reduction beyond medical laws. This may be because people seeking opioid alternatives had already accessed cannabis through medical programs, or because recreational users are not motivated by pain management.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-07069APA
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
MLA
Martins, Silvia S, et al. "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, 2025. https://doi.org/10.1016/j.drugpo.2024.104687
RethinkTHC
RethinkTHC Research Database. "The relationship of medical and recreational cannabis laws w..." RTHC-07069. Retrieved from https://rethinkthc.com/research/martins-2025-the-relationship-of-medical
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.