In Ontario, Canada, cannabis co-involvement in PTSD-related emergency department visits increased 151% from 2008 to 2022, outpacing the 58% increase in alcohol co-involvement over the same period.
PTSD clinicians, cannabis policy researchers, mental health service planners in legal cannabis jurisdictions
151% increase in cannabis-involved PTSD ER visits vs 58% for alcohol
What the researchers found
Among 381,450 PTSD ED visits in Ontario, cannabis co-involvement increased by 151% (from 0.13 to 0.33 per 100,000) between the first and last cannabis policy periods, while alcohol co-involvement increased by 58%. However, the increase was a steady upward trend not clearly tied to specific policy changes, suggesting normalization and increased access rather than legalization itself drove the increase.
Why it matters
People with PTSD are at elevated risk for cannabis use disorder. This population-level data shows that as cannabis access expanded, cannabis-related complications in PTSD patients grew substantially faster than alcohol-related complications, highlighting a population that may need targeted intervention.
The numbers in context
381,450 PTSD ED visits. 4,593 (1.29%) co-involved cannabis. 11,625 (3.05%) co-involved alcohol. Cannabis co-involvement: IRR 2.51 (151% increase, 0.13 to 0.33 per 100,000). Alcohol co-involvement: IRR 1.58 (58% increase). No significant association between specific policy periods and cannabis trend.
How the study worked
Repeated cross-sectional study using Ontario health administrative data identifying all ED visits for PTSD among residents aged 10-105 from 2008-2022 (15.7 million total). Cannabis and alcohol co-diagnoses were tracked across four cannabis policy periods, analyzed using Poisson models.
What this study cannot tell us
Administrative data using ICD codes may undercount both cannabis involvement and PTSD. Cannot determine whether cannabis contributed to the ED visit or was incidentally documented. Cannot assess whether patients were using cannabis therapeutically or recreationally. Ontario-specific findings.
How to read the evidence
Moderate evidence from a large population-based study using health administrative data over 14 years, though limited by the observational design and ICD coding constraints.
When this study was published
2025 study analyzing Ontario health data from 2008-2022 across multiple cannabis policy periods.
The bigger picture
PTSD and cannabis use have a complicated relationship: some patients report symptom relief, but cannabis use disorder rates are elevated in this population. The steady increase in cannabis-PTSD ED visits regardless of specific policy changes suggests that broader cultural shifts toward cannabis normalization, rather than legislation alone, are driving increased use among this vulnerable population.
Questions still open
- Is the increase in cannabis-PTSD ED visits driven by more cannabis use, more documentation, or both? Are PTSD patients who use cannabis having worse outcomes? Would improved access to evidence-based PTSD treatment reduce reliance on cannabis self-medication?
Common questions
Did cannabis legalization increase PTSD-related ER visits?
Should people with PTSD be concerned about cannabis use?
Read the original research
Cannabis involvement in posttraumatic stress disorder emergency department visits after cannabis legalization.
The American journal on addictions, 34(4), 404-414
Citation
Perrault-Sequeira, Laurent; Pugliese, Michael; MacDonald-Spracklin, Rachael; Xiao, Jennifer; McCarthy, Stephen; Myran, Daniel T. (2025). Cannabis involvement in posttraumatic stress disorder emergency department visits after cannabis legalization.. The American journal on addictions, 34(4), 404-414. https://doi.org/10.1111/ajad.70014
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