A natural experiment using Ontario's lottery-based cannabis retailer licensing found no significant increase in emergency department visits for cannabis, alcohol, or opioids after stores opened.
Policy makers evaluating cannabis retail regulations, public health officials, legalization researchers
No significant increase in ED visits after cannabis stores opened
What the researchers found
The allocation of recreational cannabis retailers through Ontario's randomized lottery system had no significant effect on cannabis-, alcohol-, or opioid-related emergency department visits. Sensitivity analyses using alternate diagnostic codes, co-use patterns, and cannabis-only use all confirmed the null findings.
Why it matters
A common concern about cannabis legalization is that physical retail access will increase emergency visits. This study leveraged a randomized natural experiment, providing stronger causal evidence than typical observational studies.
The numbers in context
11,156,100 adults monitored across 278 communities from January 2016 to March 2023. No significant effects on cannabis-, alcohol-, or opioid-related ED visits after retailer allocation.
How the study worked
Longitudinal study of 278 Ontario communities using health administrative data for over 11 million adults, tracked quarterly from 2016 to 2023. Ontario's lottery-based retailer licensing provided a natural experiment. Researchers used staggered difference-in-differences models weighted by inverse probability of retailer allocation.
What this study cannot tell us
Ontario-specific results may not generalize to other jurisdictions. Online cannabis sales were available before retail stores opened, potentially diluting the retail-specific effect. Possible spillover effects between communities with and without retailers.
How to read the evidence
Strong: large population-based study leveraging a randomized natural experiment with over 11 million adults tracked over 7 years
When this study was published
Published in 2025 using 2016-2023 Ontario health data
The bigger picture
The null finding suggests that physical retail access may not be the primary driver of cannabis-related health harms. Online sales, which preceded retail openings, and geographic distribution may have minimized the impact of individual store locations.
Questions still open
- Would results differ in jurisdictions without pre-existing online sales? Does retailer density matter more than simple presence? Are there subpopulations where retail access does increase ED visits?
Common questions
Why is this study design particularly strong?
Why might stores not have increased ER visits?
Read the original research
The impact of recreational cannabis retailer allocation on emergency department visits: A natural experiment utilizing lottery design.
The International journal on drug policy, 137, 104708
Citation
Bai, Yihong; Cao, Peiya; Kim, Chungah; Ienciu, Kristine; Chum, Antony. (2025). The impact of recreational cannabis retailer allocation on emergency department visits: A natural experiment utilizing lottery design.. The International journal on drug policy, 137, 104708. https://doi.org/10.1016/j.drugpo.2025.104708