Psychological Medicine
March 24, 2022
Tessa Robinson, Muhammad Usman Ali, Bethany Easterbrook et al.
61 citations
A meta-analysis of ten studies (three cohort, seven case-control) with 7,390 participants aged 12–65 found a log-linear dose-response association between cannabis use frequency and psychosis risk. The risk of psychosis significantly increased with weekly or more frequent use: weekly use showed a relative risk of 1.35 (95% CI 1.19–1.52) and daily use a relative risk of 1.76 (95% CI 1.47–2.12). Less frequent use (yearly or monthly) was not associated with a significant increase in risk. The authors conclude that frequent cannabis users are at increased risk of psychosis and recommend public health messages convey these risk thresholds.
JAMA Network Open
April 1, 2025
Jenna Matsukubo, Sarah Dickson, Jennifer Xiao et al.
7 citations
As of May 2024, 57 psilocybin dispensaries operated in Canada, located in 15 of 42 major cities (35.7%) and concentrated in Ontario and British Columbia. Most stores (61.4%) were part of a chain, 91.2% had an online presence, and all sold dried mushrooms, with many also offering microdosing capsules, chocolates, and gummies. 65.2% sold products mimicking popular food brands. Among stores with websites, 86.4% claimed mental health benefits such as alleviating anxiety, yet warnings about driving, pregnancy, or history of psychosis were rare (9.1%, 13.6%, and 31.8% respectively). The findings suggest a need for greater regulatory measures to protect the public.
Canadian Journal of Public Health
March 19, 2026
Jenna Matsukubo, Erik Loewen Friesen, Rachael MacDonald-Spracklin et al.
1 citation
Between 2024 and 2025, the number of physical psilocybin retail stores in Canada increased from 57 to 75, a 33% rise in stores per 100,000 people (0.18 to 0.24). The proportion of Canadians living within a 10-minute walk of a store rose from 1.4% to 1.7%. However, 30 of the original 57 stores closed, while 48 new ones opened, indicating rapid turnover. Two large chains operated 44% of all stores in 2025, and 97% were located in Ontario and British Columbia. In Toronto and Vancouver, 9.5% and 29.0% of residents, respectively, lived within a 10-minute walk of a store. Most stores sold dried mushrooms, microdose capsules, and infused edibles online, with 69% offering products mimicking commercial snack brands.
Journal of dual diagnosis
July 3, 2023
Benedikt Fischer, W. Hall, T. Fidalgo et al.
Cannabis use is increasingly normalized, and psychosis is a major adverse health outcome. This review identifies risk factors for cannabis-related psychosis: genetic predisposition, mental health and substance use histories, early age of first use, high frequency of use, high THC potency, mode of use, and co-use of other substances. The protective effects of CBD are uncertain. Continuous cannabis use may worsen psychosis treatment and medication effects. Combinations of risk factors further amplify the odds of adverse psychosis outcomes. Reducing these risk factors, short of abstinence, may decrease the risk of psychosis and protect cannabis users' health.