A new study published in the journal Psychological Medicine estimates that teens using cannabis are at 11 times higher risk of developing a psychotic disorder compared to teens not using cannabis.
This finding suggests that the association between cannabis and psychotic disorders may be stronger than indicated by previous research, which has relied largely on older data when cannabis was less potent than today. For context, the average THC potency of cannabis in Canada has increased from roughly 1% in 1980 to 20% in 2018.
Researchers from the University of Toronto, the Centre for Addiction and Mental Health (CAMH), and ICES, linked recent population-based survey data from over 11,000 youth in Ontario, Canada, to health service use records including hospitalizations, emergency department (ED) visits, and outpatient visits.
The study is the first to show an age-dependent association between self-reported cannabis use and subsequent psychotic disorder diagnosis, which adds to a growing body of research on the mental health risks associated with cannabis.
"We found a very strong association between cannabis use and risk of psychotic disorder in adolescence. Surprisingly, we didn’t find evidence of association in young adulthood," says lead author André McDonald, who conducted the study at ICES as part of his PhD at the University of Toronto. McDonald is now a postdoctoral fellow at the Peter Boris Centre for Addictions Research and the Michael G. DeGroote Centre for Medicinal Cannabis Research at McMaster University. "These findings are consistent with the neurodevelopmental theory that teens are especially vulnerable to the effects of cannabis."
Of the teens who were hospitalized or visited an ED for a psychotic disorder, roughly 5 in 6 had previously reported cannabis use. McDonald points out that, "the vast majority of teens who use cannabis will not develop a psychotic disorder, but according to these data, most teens who are diagnosed with a psychotic disorder likely have a history of cannabis use."
The researchers could not completely rule out reverse causation, in that teens with psychotic symptoms may have been self-medicating with cannabis before receiving a clinical diagnosis. They also could not account for potentially important factors such as genetics and […]
Teens using cannabis have 11 times higher risk of developing psychotic disorders
