Changes in Incident Schizophrenia Diagnoses Associated With Cannabis Use Disorder After Cannabis Legalization
Daniel T. Myran, Michael Pugliese, Lyndsay D. Harrison, Marco Solmi, Kelly K. Anderson, Jess G. Fiedorowicz, Yaron Finkelstein, Doug Manuel, Monica Taljaard, Colleen Webber, Peter Tanuseputro
JAMA Network Open February 1, 2025 DOI: 10.1001/jamanetworkopen.2024.57868 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Population-based cohort study Peer reviewed |
|---|---|
| Sample size | 13,588,681 |
| Population | Canadian population (13,588,681 individuals) |
| Topics | Cannabis |
| Key findings | The population-attributable fraction of cannabis use disorder associated with schizophrenia increased significantly from 3.7% in the prelegalization period to 10.3% in the postlegalization period. The authors suggest this association is an important consideration for cannabis legalization policy. |
Abstract
Key Points Question Were the liberalization of medical cannabis and the legalization of nonmedical cannabis in Canada associated with changes in the population-attributable fraction of cannabis use disorders associated with schizophrenia? Findings In this population-based cohort study comprising 13 588 681 individuals, the population-attributable fraction of cannabis use disorder associated with schizophrenia increased significantly from 3.7% in the prelegalization period to 10.3% during the postlegalization period. Meaning These findings suggest that the association between cannabis use disorders and schizophrenia is an important consideration for the legalization of cannabis.
Comparable studies
Other observational and cohort studies on cannabis, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| High-potency cannabis and the risk of psychosis People with first episode of psychosis and healthy controls from the local population | 2009 | Case-control study | n = 454 |
| Ayahuasca-Assisted Therapy for Addiction: Results from a Preliminary Observational Study in Canada Rural aboriginal population | 2013 | Observational study | |
| Impaired cognitive performance in drug free users of recreational ecstasy (MDMA) Otherwise healthy young people | 2000 | Observational | |
| Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study Individuals from the general population in Germany aged 14-24 at baseline | 2011 | Observational cohort | n = 1,923 |
| Cannabis-induced psychosis and subsequent schizophrenia-spectrum disorders: follow-up study of 535 incident cases Patients treated for cannabis-induced psychotic symptoms in Denmark between 1994 and... | 2005 | Observational cohort | n = 535 |
Citations in the library
Cited by 8
- The rising tide of drug-induced psychosis Neuropsychiatrie August 20, 2025
- The Relationship Between Cannabis Use and Schizophrenia As a Risk Factor or For Its Therapeutic Potential: A Systematic Review of Evidence Cureus September 20, 2025
- Relationships between cannabis use and mental disorders: assessing the coherence of evidence from studies with different methodologies. The Lancet Psychiatry July 1, 2026
- Emergency department use by individuals with and without psychosis after state-level cannabis legalization and commercialization Nature Mental Health June 19, 2026
- Cannabis and Mental Health: A Review. JAMA Internal Medicine May 1, 2026
and 3 more in the library
Cites 3
- State Cannabis Legalization and Psychosis-Related Health Care Utilization JAMA Network Open January 25, 2023
- Association of cannabis potency with mental ill health and addiction: a systematic review. The Lancet Psychiatry September 2022
- Potency of Δ9 -tetrahydrocannabinol and other cannabinoids in cannabis in England in 2016: Implications for public health and pharmacology. Drug Testing and Analysis April 2018