Teen cannabis use linked to double the risk of psychosis

A large-scale longitudinal study published in JAMA Health Forum has found that cannabis use during adolescence is associated with substantially higher risks of developing serious mental health disorders in young adulthood. Researchers analysed electronic health records from 463,396 teenagers aged 13 to 17 in the Kaiser Permanente health system in Northern California, tracking them between 2016 and 2023 and following outcomes until age 25 to 26. Critically, the study excluded adolescents who already showed symptoms of mental illness before cannabis use, strengthening the case that cannabis exposure may be a contributing risk factor — though researchers note the findings reflect association, not proven causation. Cannabis use preceded psychiatric diagnoses by an average of 1.7 to 2.3 years, according to the study authors.

The study was conducted by researchers from Kaiser Permanente, the Public Health Institute's Getting it Right from the Start programme, the University of California San Francisco, and the University of Southern California, and was funded by NIH's National Institute on Drug Abuse. Full citation: Silver L, et al. "Adolescent Cannabis Use and Incident Psychiatric Disorders." JAMA Health Forum, 2026. DOI: 10.1001/jamahealthforum.2026.0246.

Note: A separate study published in Lancet Psychiatry (2026) examined whether cannabis alleviates anxiety and other mental health conditions — a related but distinct question from the psychosis risk findings above.

• 463,396 teenagers aged 13–17 studied in Kaiser Permanente's Northern California health system • Study tracked participants between 2016 and 2023, with outcomes followed to age 25–26 • Adolescents with pre-existing mental illness symptoms were excluded from the analysis • Cannabis use preceded psychiatric diagnoses by an average of 1.7 to 2.3 years • Cannabis use was associated with double the risk of psychotic and bipolar disorders • Study published in JAMA Health Forum; DOI: 10.1001/jamahealthforum.2026.0246

For Caribbean policymakers navigating cannabis reform, this study introduces evidence that cannot be sidelined. The region already shoulders a disproportionate burden from cannabis-related drug use disorders, and these findings suggest that without robust youth protections built into any legalisation framework, the public health costs could be severe. Jamaica — which legalised personal possession in 2015 and is currently reviewing its Cannabis Licensing Authority framework — and Trinidad and Tobago — where a Cannabis Commission has been examining full legalisation since 2023 — are among the territories where enforceable age limits and potency caps remain unresolved. Disability-adjusted life years linked to drug use disorders in the Americas nearly tripled between 2000 and 2021 — a trajectory that cannabis commercialisation, without safeguards, risks accelerating.

"In the Caribbean, Central America, and South America, cannabis and cocaine use are the main contributors to drug use disorders — with 17.7 million people across the Americas living with a drug use disorder in 2021 and disability-adjusted life years nearly tripling between 2000 and 2021."

— Pan American Health Organisation (PAHO), Pan American Journal of Public Health, January 2026

Predictions: • Caribbean policymakers will face increased pressure to add youth-protection clauses to pending cannabis legislation following international coverage of this study. • Trinidad and Tobago's Cannabis Commission is likely to reference mental health risk data in its next public report. • Jamaica's Cannabis Licensing Authority review may incorporate potency cap discussions in its 2026 regulatory update.

Viewpoint: For Caribbean health officials, this study arrives as a warning that the region's existing cannabis burden may deepen. PAHO has already identified cannabis as one of the primary drivers of drug use disorders across the Caribbean, Central America, and South America — and this research suggests harm is taking root earlier than previously understood. With the Americas already recording nearly 78,000 drug-related deaths annually and DALYs nearly tripling between 2000 and 2021, adolescent mental health screening and early intervention programmes are not optional extras — they are urgent infrastructure.

Viewpoint: Several Caribbean territories are actively debating or advancing cannabis reform. This study — tracking nearly half a million teenagers over nearly a decade and excluding those with pre-existing mental illness — strengthens the scientific case for embedding enforceable age limits, potency caps, and bans on youth-targeted marketing into any legalisation framework from the outset. Reform without these protections is not a balanced approach; it is an uncontrolled experiment conducted on the region's young people.

Viewpoint: Researchers are careful to frame these findings as association, not proven causation. Yet the study's design — longitudinal, large-scale, and controlled for pre-existing conditions — represents some of the strongest evidence to date. Cannabis use preceded psychiatric diagnoses by an average of 1.7 to 2.3 years, a sequencing that meaningfully advances the research beyond correlation.

Viewpoint: Not all observers accept that these findings translate directly to Caribbean contexts. The study draws entirely from a Northern California HMO population — a demographic, healthcare, and cultural setting that differs substantially from the Caribbean. Reform advocates and harm-reduction researchers argue that regulated legalisation, with age restrictions, may actually reduce youth access compared to unregulated illicit markets currently operating across the region. Meanwhile, Rastafari communities maintain that cannabis use holds constitutionally protected spiritual and cultural significance, and that risk-framing rooted in US clinical data should not override indigenous rights and lived experience. Economists further note that legalisation generates tax revenue that could fund the very mental health infrastructure public health advocates are calling for. These perspectives do not diminish the study's findings — but they caution against treating a single dataset as sufficient grounds for foreclosing a complex regional conversation.