A recent study conducted by researchers from the Centre for Addiction and Mental Health (CAMH), the University of Toronto, and ICES has revealed a concerning link between teen cannabis use and the development of psychotic disorders. The study, titled ‘Age-dependent association of cannabis use with risk of psychotic disorder,’ published in the journal Psychological Medicine, indicates that teenagers who use cannabis are at an alarming 11 times higher risk of experiencing a psychotic disorder compared to their non-using counterparts.
The findings of this study shed light on a potentially stronger association between cannabis use and psychotic disorders than previously believed. Past research had primarily relied on outdated data when cannabis had lower potency levels, unlike the current average THC (tetrahydrocannabinol) potency in Canada, which has risen from 1% in 1980 to 20% in 2018.
The research team analyzed recent survey data from over 11,000 young individuals in Ontario, Canada, connecting it with health service records including hospitalizations, emergency department visits, and outpatient visits. This study marks the first to demonstrate an age-dependent correlation between self-reported cannabis use during adolescence and subsequent diagnosis of a psychotic disorder, contributing to the growing body of evidence highlighting the mental health risks associated with cannabis consumption.
Lead author Dr. André McDonald, who spearheaded the study during his PhD training at the Institute for Mental Health Policy Research at CAMH and the University of Toronto, and is currently a postdoctoral fellow at McMaster University, emphasized, ‘We found a very strong association between cannabis use and the risk of psychotic disorder in adolescence. Surprisingly, we didn’t find evidence of association in young adulthood.’ McDonald further explained that while most teens who use cannabis will not develop a psychotic disorder, a significant proportion of teens diagnosed with such disorders have a history of cannabis use.
Although the study could not definitively rule out reverse causation, suggesting that teens with psychotic symptoms might have used cannabis as a form of self-medication prior to diagnosis, it underscores the importance of considering various factors when assessing the impact of cannabis on mental health.
