5 Things to Know About Cannabis and Psychosis

1. Cannabis potency 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.
2. High-potency and regular cannabis use is linked to increased 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%.
3. Cannabis-induced psychosis and cannabis use disorder increase the 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 requires stopping cannabis and taking medication — 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 the primary 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 options may help with 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.

“Cannabis from the 2000s is not the same as in 2025,” said coauthor Dr. Nicholas Fabiano, MD, resident and researcher with the Department of Psychiatry, University of Ottawa, Ottawa, Ontario. “THC content has increased by 5 times. This is likely a significant driver in the increasing link between cannabis use and schizophrenia.”