Cannabis Legalization Hit Psychiatric Teens Hardest — 4x More Cannabis Disorders
After Massachusetts legalized recreational cannabis sales, THC-positive rates among adolescent psychiatric ER patients surged from 5% to 17%, and cannabis use disorders jumped from 3% to 12% — a 4.6-fold increase.
Quick Facts
What This Study Found
THC positivity increased from 32.4% to 36.3% overall (p<.001). Adolescents (12-17) had the largest increase: from 5% to 17.3% (AOR=4.32). Only adolescents showed a significant increase in cannabis use disorders: from 3.2% to 12.1% (AOR=4.63). Adults aged 26-49 showed a modest THC positivity increase (AOR=1.24).
Key Numbers
7,350 presentations. Overall THC+: 32.4% → 36.3%. Adolescents: THC+ 5% → 17.3% (AOR=4.32). Adolescent CUD: 3.2% → 12.1% (AOR=4.63). Adults 26-49: THC+ 37.7% → 42.5% (AOR=1.24). Adults 18-25 and 50-70: no significant changes.
How They Did This
Cross-sectional analysis of 7,350 unique presentations to a psychiatric emergency service at a tertiary hospital in Massachusetts. Compared pre-commercialization (Jan 2017-Nov 2018) to post-commercialization (Nov 2018-Dec 2019) periods. Logistic regressions controlled for sex, race, and ethnicity across age groups.
Why This Research Matters
Psychiatric patients are among the most vulnerable to cannabis harms, and adolescents with psychiatric conditions are especially at risk. This study provides direct evidence that cannabis commercialization disproportionately affects the youngest, most vulnerable psychiatric patients.
The Bigger Picture
The 4.6-fold increase in adolescent cannabis disorders in psychiatric ER patients is alarming. These are already high-risk youth, and increased cannabis exposure may worsen psychiatric outcomes. This has direct implications for how legalization is implemented and what protections are needed for vulnerable populations.
What This Study Doesn't Tell Us
Single hospital, single state. Pre/post comparison without control group. Short post-commercialization period (13 months). THC positivity doesn't indicate cannabis caused the ER visit. Psychiatric ER patients are a specific, high-risk population.
Questions This Raises
- ?What safeguards could protect psychiatric adolescents during legalization?
- ?Are there longer-term psychiatric consequences?
- ?Do other states show similar patterns?
Trust & Context
- Key Stat:
- Evidence Grade:
- Single-center pre-post study with objective THC testing — provides compelling evidence of temporal association though cannot prove causation.
- Study Age:
- Published in 2026, examining the early impact of Massachusetts cannabis commercialization (2018).
- Original Title:
- Effects of Legalizing Recreational Cannabis Sales on Cannabis Use and Cannabis-Related Disorder Among Presentations to a Psychiatric Emergency Service.
- Published In:
- American journal of preventive medicine, 70(1), 108142 (2026)
- Authors:
- Foo, Cheryl Y S, Potter, Kevin(7), Wright, Abigail C(3), Evins, A Eden, Donovan, Abigail L, Levy, Sharon, Mueser, Kim T, Cather, Corinne
- Database ID:
- RTHC-08265
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Does cannabis legalization affect teens with mental health issues?
This study suggests yes — after Massachusetts legalized cannabis sales, THC-positive rates among teen psychiatric ER patients jumped from 5% to 17%, and cannabis disorders surged from 3% to 12%. Teens were far more affected than adults.
Why are psychiatric teens more vulnerable?
Psychiatric conditions can increase vulnerability to substance use, and adolescent brains are still developing. The combination of greater cannabis accessibility and psychiatric vulnerability appears to create a compounding risk that standard age restrictions alone don't prevent.
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Cite This Study
https://rethinkthc.com/research/RTHC-08265APA
Foo, Cheryl Y S; Potter, Kevin; Wright, Abigail C; Evins, A Eden; Donovan, Abigail L; Levy, Sharon; Mueser, Kim T; Cather, Corinne. (2026). Effects of Legalizing Recreational Cannabis Sales on Cannabis Use and Cannabis-Related Disorder Among Presentations to a Psychiatric Emergency Service.. American journal of preventive medicine, 70(1), 108142. https://doi.org/10.1016/j.amepre.2025.108142
MLA
Foo, Cheryl Y S, et al. "Effects of Legalizing Recreational Cannabis Sales on Cannabis Use and Cannabis-Related Disorder Among Presentations to a Psychiatric Emergency Service.." American journal of preventive medicine, 2026. https://doi.org/10.1016/j.amepre.2025.108142
RethinkTHC
RethinkTHC Research Database. "Effects of Legalizing Recreational Cannabis Sales on Cannabi..." RTHC-08265. Retrieved from https://rethinkthc.com/research/foo-2026-effects-of-legalizing-recreational
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.