Analysis of nearly 69,000 suicide and undetermined-intent deaths found that more liberal cannabis policies were associated with higher rates of both cannabis and opioid involvement in these deaths.
Policymakers evaluating cannabis legislation and researchers studying substance use in deaths of despair.
More restrictive cannabis policies were linked to 12-13% lower odds of cannabis and opioid involvement in suicide deaths
What the researchers found
Cannabis involvement in death was associated with increased odds of opioid involvement (AOR=1.29). More restrictive cannabis policies were associated with reduced odds of both cannabis involvement (AOR=0.87 per 10% policy increase) and opioid involvement (AOR=0.88 per 10% policy increase) in suicide and undetermined-intent deaths.
Why it matters
This challenges the hypothesis that liberalizing cannabis policies might reduce opioid deaths through substitution. Instead, the data suggest that more permissive cannabis environments are associated with higher involvement of both substances in deaths of despair.
The numbers in context
68,924 decedents from suicide and undetermined intent deaths (2003-2018). Cannabis involvement increased odds of opioid involvement: AOR=1.29 (95% CI: 1.22-1.37). A 10% more restrictive cannabis policy: AOR=0.87 for cannabis involvement, AOR=0.88 for opioid involvement.
How the study worked
Repeated cross-sectional study using restricted-access National Violent Death Reporting System data (2003-2018) linked to the Cannabis Policy Scale measuring state-level cannabis policy permissiveness. Mixed effects logistic regression analyzed 68,924 decedents across states that expanded from 7 to 41 during the study period.
What this study cannot tell us
Observational design cannot prove cannabis policies cause these deaths. Not all states participated throughout the study period. Toxicology testing practices vary across jurisdictions. Cannabis involvement does not mean cannabis caused the death.
How to read the evidence
Moderate: large dataset with validated policy scale and adjusted models, but observational design and varying state participation limit causal inference.
When this study was published
2025 study using 2003-2018 data.
The bigger picture
The relationship between cannabis policy, cannabis use, opioid use, and deaths of despair is more complex than simple substitution theories suggest. These findings add important data to the ongoing policy debate about cannabis legalization and public health.
Questions still open
- Does cannabis use directly contribute to suicide risk, or does it mark a population already at higher risk? Would the relationship between cannabis policy and opioid involvement hold in more recent data after wider legalization?
Common questions
Does this mean cannabis legalization increases suicides?
Were cannabis and opioids found together in these deaths?
Read the original research
Cannabis Policies, Cannabis, and Opioids in Suicide and Undetermined Intent Death.
American journal of preventive medicine, 68(3), 475-484
Citation
Lira, Marlene C; Pacula, Rosalie Liccardo; Smart, Rosanna; Pessar, Seema Choksy; Blanchette, Jason; Naimi, Timothy S. (2025). Cannabis Policies, Cannabis, and Opioids in Suicide and Undetermined Intent Death.. American journal of preventive medicine, 68(3), 475-484. https://doi.org/10.1016/j.amepre.2024.11.009