Cannabis and Psychosis

Journal of Psychiatry Reform vol 12 #15, December 1, 2025

Sophie Li, Marco Solmi, Daniel T. Myran and Nicholas Fabiano
CMAJ August 11, 2025 197 (27) E810; DOI: https://doi.org/10.1503/cmaj.250659

The potency of cannabis is increasing
The tetrahydrocannabinol (THC) content of cannabis has roughly quintupled in the past 2 decades, from around 4%
in the 2000s to more than 20% in most legal dried cannabis in Canada by 2023.1

High-potency and regular cannabis use are associated with elevated risk of psychosis
The lifetime occurrence of cannabis-induced psychosis symptoms is estimated to be 0.47% among people who use
cannabis.2 The risk of cannabis-induced psychosis is elevated among those using high-potency THC (a product with > 10% THC) and those who use cannabis frequently, are younger, or are male.3 4
Evidence also suggests that a history of a mental disorder (e.g., bipolar disorder, depression, anxiety) increases the risk of psychosis. 2
More than half of patients with cannabis-associated psychosis recover within 24 hours, but those with prolonged symptoms (>1 wk) or a history of psychosis have hospitalization rates ranging from 54% to 76%.

People with cannabis-induced psychosis and cannabis use disorder are at high risk of schizophrenia

A population-based retrospective cohort study of 9.8 million people in Ontario, Canada, found that people with an emergency department visit for cannabis use or cannabis-induced psychosis were at a 14.3-fold and 241.6-fold higher risk of developing a schizophrenia-spectrum disorder within 3 years than the general population, respectively.4

Treatment for cannabis-induced psychosis involves cessation and antipsychotic agents

Ongoing cannabis use after first-episode psychosis is associated with a greater incidence of return of symptoms.3 The current mainstay of intervention in cannabis-induced psychosis is abstinence from cannabis.5
Second generation antipsychotic medications may be prescribed for patients with severe and persistent symptoms, with theprimary goal of alleviating acute symptoms. Once the acute symptoms have resolved, a gradual tapering or
discontinuation of the antipsychotic medication can be considered.5

Behavioural interventions may aid in cannabis cessation

Motivational interviewing can increase treatment engagement, while cognitive behavioural therapy can build skills to
resist cravings and urges to use cannabis. These interventions can be delivered by physicians or psychologists, and
lead to reduction in cannabis use, reduction of psychiatric symptom burden, and improvement of psychosocial
functioning.5

Footnotes
Competing interests: Marco Solmi reports honoraria and consulting fees from Angelini, AbbVie, Bausch
Health, Boehringer Ingelheim, Lundbeck, Otsuka, and Teva. No other competing interests were declared.
This article has been peer reviewed.

This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY-NC-ND 4.0) licence, which permits use, distribution and reproduction in any medium, provided that the original
publication is properly cited, the use is noncommercial (i.e., research or educational use), and no modifications or adaptations are made.

References

1. Myran DT, Pugliese M, Harrison LD, et al. Changes in incident schizophrenia diagnoses associated with cannabis use disorder after cannabis legalization. JAMA Netw Open 2025;8:e2457868. Google Scholar

2.. Schoeler T, Ferris J, Winstock AR. Rates and correlates of cannabis-associated psychotic symptoms in over 230,000 people who use cannabis. Transl Psychiatry 2022;12:369. PubMed Google Scholar

3. Schoeler T, Monk A, Sami MB, et al. Continued versus discontinued cannabis use in patients with psychosis: a systematic review and meta-analysis. Lancet Psychiatry 2016;3:215–25. PubMed Google Scholar

4. Myran DT, Harrison LD, Pugliese M, et al. Transition to schizophrenia spectrum disorder following emergency department visits due to substance use with and without psychosis. JAMA Psychiatry 2023;80:1169–74. PubMed Google Scholar

5. D’Souza DC,  DiForti M, Ganesh S, et al. Consensus paper of the WFSBP task force on cannabis, cannabinoids and psychosis. World J Biol Psychiatry 2022;23:719–42.