Teens who started cannabis before age 15 and used frequently had significantly higher rates of medical care for mental and physical health conditions in young adulthood, even after adjusting for 32 confounders measured from birth.
Parents, pediatricians, school counselors, and policymakers focused on adolescent cannabis prevention.
86% higher odds of physical health care for early/frequent teen users
What the researchers found
Three adolescent cannabis patterns were identified: nonuse (60%), late-onset after 15 (20%), and early/frequent before 15 (20%). Early/frequent users had 51% higher odds of mental health care (OR 1.51), 57% higher odds of common mental disorder care (OR 1.57), and 86% higher odds of physical health care (OR 1.86) compared to nonusers. Late-onset users showed increased physical but not mental health care utilization.
Why it matters
This is among the strongest evidence linking adolescent cannabis patterns to concrete healthcare outcomes. By adjusting for 32 confounders measured before cannabis exposure began, it addresses the concern that pre-existing factors rather than cannabis itself drive the association.
The numbers in context
N = 1,591 (51.4% female). 3 trajectory groups: nonuse 59.6%, late-onset 20.0%, early/frequent 20.4%. Early/frequent vs nonuse: mental disorder OR 1.51, common mental disorder OR 1.57, any physical condition OR 1.86, injuries OR 1.41, other physical diseases OR 1.47. Late-onset: physical condition OR 1.63 only.
How the study worked
Population-based birth cohort from the Quebec Longitudinal Study of Child Development linked to administrative medical databases. Self-reported cannabis use at ages 12, 13, 15, and 17. Medical care utilization tracked from ages 18-23. Analyses adjusted for 32 individual, family, and community-level confounders measured from birth to age 12 using overlap weights.
What this study cannot tell us
Canadian birth cohort may not generalize to other populations. Medical care utilization reflects healthcare-seeking behavior, not just health status. Self-reported cannabis use may be underreported. Administrative data captures diagnoses given during visits but may miss undiagnosed conditions.
How to read the evidence
Birth cohort linked to administrative data with 32 pre-exposure confounders. Among the strongest observational designs possible for this question. Published in JAMA Network Open.
When this study was published
Published in 2025 in JAMA Network Open with follow-up to age 23.
The bigger picture
The distinction between early/frequent and late-onset patterns is critical for policy. Late-onset users (starting after 15) did not show excess mental health care utilization, suggesting that delaying initiation may be as important as preventing use entirely.
Questions still open
- Would these patterns hold in jurisdictions with different healthcare access? Does the increased physical health care utilization reflect injuries related to cannabis use or other factors?
Common questions
Does late-onset teen cannabis use also cause problems?
How do the researchers know it is cannabis and not other factors?
Read the original research
Health Service Use Among Young Adults With a History of Adolescent Cannabis Use.
JAMA network open, 8(10), e2539977
Citation
Martínez, Pablo; Chadi, Nicholas; Castellanos-Ryan, Natalie; Vergunst, Francis; Dorais, Marc; Séguin, Jean R; Vitaro, Frank; Temcheff, Caroline; Tremblay, Richard E; Boivin, Michel; Côté, Sylvana M; Geoffroy, Marie-Claude; Orri, Massimiliano. (2025). Health Service Use Among Young Adults With a History of Adolescent Cannabis Use.. JAMA network open, 8(10), e2539977. https://doi.org/10.1001/jamanetworkopen.2025.39977
Explore the wider topic
- How to Talk to Your Teenager About Weed (Without Losing Them)
- My Kid's Friends Smoke Weed: A Parent's Guide
- I Smoke Weed But Don't Want My Kids To: Navigating the Hypocrisy
- Quitting Weed as a Parent: Why It Is the Hardest and Most Important Quit
- Quitting Weed as a Teen or Young Adult
- My Kid Is Smoking Weed: A Parent's Guide