Cannabis Legalization Linked to More Positive Drug Tests in Emergency Rooms
Cannabis-positive urine tests among ER patients increased everywhere from 2008-2019, but states with recreational cannabis laws saw the biggest jump.
Quick Facts
What This Study Found
Using biological urine drug screens rather than self-report, recreational cannabis law (RCL) enactment was associated with a 2.9% increase in cannabis-positive tests among ER patients, while medical cannabis laws alone were associated with a 0.8% increase. Overall prevalence rose from about 16-18% to 26-34% across all state categories.
Key Numbers
No-law states: 16.4% to 25.6%. MCL-only states: 16.6% to 27.6%. RCL states: 18.2% to 33.8%. MCL effect: +0.8% (95% CI 0.4-1.0). RCL effect: +2.9% (95% CI 2.5-3.3).
How They Did This
Staggered-adoption difference-in-difference analysis of VHA emergency department patients aged 18-75 from 2008-2019. Used urine drug screen results (biological measure) rather than self-report to reduce social desirability bias.
Why This Research Matters
Previous studies relied on self-reported cannabis use, which could be biased by changing stigma. By using biological urine tests, this study provides stronger evidence that legalization genuinely increased cannabis use, not just willingness to report it.
The Bigger Picture
Cannabis use was increasing nationally regardless of legal status, but legalization accelerated the trend. The biological measurement approach addresses a key criticism of earlier survey-based research.
What This Study Doesn't Tell Us
VHA patients (predominantly male, older) may not represent the general population. Urine drug screens detect recent use but don't quantify frequency or amount. Study period ended in 2019; more recent trends not captured.
Questions This Raises
- ?Has the trend continued or accelerated since 2019?
- ?Are the increases in use associated with proportional increases in cannabis use disorder?
- ?Do the findings hold in non-veteran populations?
Trust & Context
- Key Stat:
- Recreational legalization associated with 2.9% increase in positive drug tests
- Evidence Grade:
- Large longitudinal study using objective biological measures and rigorous difference-in-difference methodology.
- Study Age:
- 2025 study
- Original Title:
- Cannabis legalization and increasing cannabis use in the United States: Data from urine toxicology testing in emergency room patients.
- Published In:
- The International journal on drug policy, 138, 104765 (2025)
- Authors:
- Fink, David S(13), Samples, Hillary(5), Malte, Carol A(4), Olfson, Mark, Wall, Melanie M, Alschuler, Daniel M, Simpson, Tracy, Mannes, Zachary, Saxon, Andrew J, Hasin, Deborah S
- Database ID:
- RTHC-06458
Evidence Hierarchy
Follows a group of people over time to track how outcomes develop.
What do these levels mean? →Frequently Asked Questions
Why use drug tests instead of surveys?
As cannabis becomes more accepted, people may be more willing to report use on surveys, making it look like use increased when only reporting changed. Urine tests provide an objective measure that isn't affected by changing attitudes.
Did cannabis use increase even in states without legalization?
Yes. Cannabis-positive tests increased from 16.4% to 25.6% even in states with no cannabis laws, suggesting a national trend that legalization amplified.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-06458APA
Fink, David S; Samples, Hillary; Malte, Carol A; Olfson, Mark; Wall, Melanie M; Alschuler, Daniel M; Simpson, Tracy; Mannes, Zachary; Saxon, Andrew J; Hasin, Deborah S. (2025). Cannabis legalization and increasing cannabis use in the United States: Data from urine toxicology testing in emergency room patients.. The International journal on drug policy, 138, 104765. https://doi.org/10.1016/j.drugpo.2025.104765
MLA
Fink, David S, et al. "Cannabis legalization and increasing cannabis use in the United States: Data from urine toxicology testing in emergency room patients.." The International journal on drug policy, 2025. https://doi.org/10.1016/j.drugpo.2025.104765
RethinkTHC
RethinkTHC Research Database. "Cannabis legalization and increasing cannabis use in the Uni..." RTHC-06458. Retrieved from https://rethinkthc.com/research/fink-2025-cannabis-legalization-and-increasing
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.