Rates and correlates of cannabis-associated psychotic symptoms in over 230,000 people who use cannabis

About 1 in 200 people who use cannabis (0.47%) experience acute psychotic symptoms—hallucinations or paranoia—severe enough to require emergency medical treatment at some point in their lives, based on data from 233,475 users across multiple countries. Risk is higher among young individuals (2.66 times), those in Denmark (3.01 times), users of high-potency resin (2.11 times), those mixing cannabis with tobacco (2.15 times), and people with pre-existing mental health diagnoses: psychosis (14.01 times), bipolar disorder (4.30 times), anxiety (2.92 times), and depression (2.68 times). The findings suggest certain groups are especially vulnerable to cannabis-induced psychotic symptoms.

Study at a glance

Abstract

Cannabis, a widely used psychoactive substance, can trigger acute cannabis-associated psychotic symptoms (CAPS) in people who use cannabis (PWUC). To assess rates and correlates of CAPS requiring emergency medical treatment, we analyzed data from an international sample of PWUC (n = 233,475). We found that 0.47% (95%CI 0.42; 0.52) PWUC reported lifetime occurrence of CAPS, defined as the occurrence of hallucinations and/or paranoia requiring emergency medical treatment following the use of cannabis. A range of factors correlated with risk of CAPS in the last year: higher rates were observed in young individuals [risk ratio (RR) 2.66, compared to older PWUC] and those residing in Denmark (RR 3.01, compared to PWUC from other countries). Furthermore, risk was elevated in those using predominantly high-potency resin (RR 2.11, compared to PWUC using herbal cannabis), those mixing cannabis with tobacco (RR 2.15, compared to PWUC not mixing with tobacco) and those with a diagnosis of psychosis (RR 14.01), bipolar (RR 4.30), anxiety (RR 2.92) and depression (RR 2.68), compared to individuals without a mental health diagnosis. Taken together, acute self-limiting psychotic symptoms in the context of cannabis use may occur in about 1 in 200 PWUC's lifetime. Some individuals could be particularly sensitive to the adverse psychological effects of cannabis, such as young individuals or those with pre-existing mental health vulnerabilities. In light of the movements towards legalization of recreational cannabis, more research should focus on the potential harms related to cannabis use, to educate PWUC and the public about risks related to its use.