Arizona dispensary lottery shows medical marijuana access increased cannabis ER visits by 45%
Using a natural experiment from Arizona's dispensary lottery, researchers found that zip codes assigned a dispensary saw cannabis-related ER visits increase by approximately 45% over four years.
Quick Facts
What This Study Found
Zip codes winning a dispensary license saw cannabis-related ER visits increase approximately 45% relative to non-winning zip codes over four years. Weak evidence of increased opioid-related visits was also found. The lottery design provides unusually strong causal evidence for the effect of dispensary access.
Key Numbers
Approximately 45% increase in cannabis ER visits in winning zip codes vs. non-winning over 4 years. 36 winning vs. 48 losing zip codes across 69 contested areas. Likely underestimates due to spillover effects.
How They Did This
Natural experiment using Arizona's August 2012 lottery for medical marijuana dispensary licenses. 36 winning zip codes compared to 48 losing zip codes using propensity score weighting. ER discharge data from 2010-2016 for cannabis, opioid, alcohol, and cocaine-related visits.
Why This Research Matters
The lottery design approximates a randomized experiment, providing stronger causal evidence than typical dispensary studies about the health effects of expanding medical marijuana access.
The Bigger Picture
While dispensary access aims to provide safe, regulated cannabis, increased ER utilization suggests that expanded access also brings health system costs that policymakers should anticipate.
What This Study Doesn't Tell Us
ER discharge data may not capture all cannabis-related presentations; spillover between neighboring zip codes likely attenuates the measured effect; cannot distinguish between more use vs. more acute reactions; Arizona-specific context.
Questions This Raises
- ?Are the ER visits driven by new users, higher-potency products, or edible miscalculations?
- ?Do the ER visits represent serious harm or mostly precautionary visits?
Trust & Context
- Key Stat:
- ~45% increase in cannabis ER visits in dispensary zip codes over 4 years
- Evidence Grade:
- Strong quasi-experimental design using randomized lottery allocation, though limited by ecological data and spillover concerns.
- Study Age:
- Published in 2020.
- Original Title:
- A lottery test of the effect of dispensaries on emergency room visits in Arizona.
- Published In:
- Health economics, 29(8), 854-864 (2020)
- Authors:
- Conyers, Gregory, Ayres, Ian
- Database ID:
- RTHC-02476
Evidence Hierarchy
Watches what happens naturally without intervening.
What do these levels mean? →Frequently Asked Questions
Why is this study particularly credible?
Arizona allocated dispensary licenses by lottery, creating a natural experiment where some zip codes randomly got dispensaries and others did not. This randomization mimics a controlled experiment and reduces the bias that affects most dispensary studies.
Does this mean dispensaries are harmful?
The study shows dispensary access increased ER visits for acute cannabis causes. Whether these visits represent serious harm or precautionary presentations (like anxiety episodes) is not addressed. The finding suggests expanded access has health system impacts that should be planned for.
Read More on RethinkTHC
- 420-sober-survival-guide
- CBT-cannabis-recovery
- cannabis-relapse-cycle-pattern
- cold-turkey-vs-taper-quit-weed
- dating-sober-after-quitting-weed
- exercise-quitting-weed-anxiety-brain
- grieving-quitting-weed-loss
- help-someone-quit-weed
- how-to-quit-weed
- journaling-weed-withdrawal
- marijuana-anonymous-SMART-recovery-compare
- meditation-mindfulness-weed-withdrawal
- partner-still-smokes-weed
- partner-still-smokes-weed-quitting
- pink-cloud-sobriety-cannabis
- quit-weed-cold-turkey
- quit-weed-or-cut-back-which-is-better
- quit-weed-regret-went-back
- quitting-weed-20s
- quitting-weed-30s
- quitting-weed-after-years
- quitting-weed-during-crisis-divorce-job-loss
- quitting-weed-exercise
- quitting-weed-grief-loss-coping
- quitting-weed-legal-state
- quitting-weed-success-stories
- quitting-weed-triggers-environment
- relapsed-smoking-weed-what-to-do
- relapsed-weed
- should-i-quit-weed
- sober-music-festival-concert-without-weed
- supplements-weed-withdrawal
- telling-friends-quitting-weed
- weed-relapse-prevention-plan
- weed-relapse-why-it-happens
- weed-ritual-replacement
- weed-ruined-relationships
- weed-social-media-triggers-quit
Cite This Study
https://rethinkthc.com/research/RTHC-02476APA
Conyers, Gregory; Ayres, Ian. (2020). A lottery test of the effect of dispensaries on emergency room visits in Arizona.. Health economics, 29(8), 854-864. https://doi.org/10.1002/hec.4013
MLA
Conyers, Gregory, et al. "A lottery test of the effect of dispensaries on emergency room visits in Arizona.." Health economics, 2020. https://doi.org/10.1002/hec.4013
RethinkTHC
RethinkTHC Research Database. "A lottery test of the effect of dispensaries on emergency ro..." RTHC-02476. Retrieved from https://rethinkthc.com/research/conyers-2020-a-lottery-test-of
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.