Medical cannabis laws were associated with 31 more cannabis use disorder diagnoses per 100,000 insured adults per quarter, while recreational laws were associated with increased cannabis poisoning.
Policymakers, psychiatrists, health economists, and cannabis legalization researchers.
Medical cannabis laws associated with 31 additional CUD diagnoses per 100,000 insured adults per quarter
What the researchers found
Among 110 million commercially insured adults (2011-2021), medical cannabis laws were associated with increases of 31.09 CUD diagnoses and 0.76 cannabis poisoning diagnoses per 100,000 enrollees per quarter. Recreational cannabis laws were associated with 0.34 additional cannabis poisoning diagnoses per quarter. CUD increases were larger among women and adults aged 35-44. Opening medical dispensaries or allowing home cultivation did not show significant independent effects.
Why it matters
Published in JAMA Psychiatry, this is one of the largest and most rigorous studies linking cannabis policy changes to clinical diagnoses, using claims data from over 110 million commercially insured adults.
The numbers in context
110,256,536 enrollees (52% female, mean age 41.0). MCL: +31.09 CUD diagnoses (95% CI: 20.20-41.99; p<0.001) and +0.76 poisoning (95% CI: 0.52-1.00; p<0.001) per 100k/quarter. RCL: +0.34 poisoning (95% CI: 0.19-0.48; p<0.001). CUD increases larger in women and ages 35-44.
How the study worked
Staggered adoption difference-in-differences analysis using the Merative MarketScan Commercial Claims database (2011-2021) across all 50 states and DC. Event studies estimated magnitude by year-quarter relative to policy implementation. Subgroup analyses by sex and age.
What this study cannot tell us
Commercially insured population may not represent uninsured or Medicaid populations. Cannot distinguish whether increased diagnoses reflect more CUD or more clinical detection due to reduced stigma. Claims data may include coding changes over time. Sensitivity analysis confirmed results held when excluding COVID-era data.
How to read the evidence
Very large cohort (110M+ enrollees), rigorous difference-in-differences design, published in JAMA Psychiatry. Sensitivity analyses confirmed robustness.
When this study was published
2025 JAMA Psychiatry publication with 2011-2021 data.
The bigger picture
While cannabis use increases modestly after legalization, this study shows the downstream clinical consequences (diagnosed CUD and poisoning) are measurable at the population level and concentrated in demographics not traditionally considered high-risk for cannabis problems.
Questions still open
- Is the CUD increase driven by more people developing the disorder, or more people seeking treatment as stigma decreases?
- Why were women and 35-44 year olds disproportionately affected?
Read the original research
Association of State Cannabis Legalization With Cannabis Use Disorder and Cannabis Poisoning.
JAMA psychiatry, 82(3), 228-236
Citation
Jayawardhana, Jayani; Hou, Jialin; Freeman, Patricia; Talbert, Jeffery C. (2025). Association of State Cannabis Legalization With Cannabis Use Disorder and Cannabis Poisoning.. JAMA psychiatry, 82(3), 228-236. https://doi.org/10.1001/jamapsychiatry.2024.4145