Cannabis Legalization Linked to More Positive Drug Tests in Emergency Rooms | Research

The takeaway

Cannabis-positive urine tests among ER patients increased everywhere from 2008-2019, but states with recreational cannabis laws saw the biggest jump.

Policy researchers; public health officials monitoring legalization impacts; epidemiologists studying substance use trends.

Recreational legalization associated with 2.9% increase in positive drug tests

What the researchers 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.

Why it 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 numbers in context

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 the study worked

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.

What this study cannot 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.

How to read the evidence

Large longitudinal study using objective biological measures and rigorous difference-in-difference methodology.

When this study was published

2025 study

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.

Questions still open

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?

Common 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 the original research

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

View on PubMed ↗Publisher’s paper ↗

Citation

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