“Many have hypothesized that adolescence is a more sensitive risk period than adulthood for the effect of cannabis use on psychotic disorder development, yet prior to this study, little epidemiologic evidence existed to support this view,” the authors wrote.
The data also suggest that cannabis use is “more strongly associated with more severe psychotic outcomes, as the strength of association during adolescence increased markedly when we restricted the outcome to hospitalizations and ED visits (the most severe types of health service use),” the investigators noted.
The authors noted several limitations. For instance, it’s unclear to what extent unmeasured confounders including genetic predisposition, family history of psychotic disorders, and trauma might have biased the results. In addition, they could not assess the potential confounding impact of genetic predisposition to psychotic disorders. The possibility of reverse causality also cannot be ruled out. It’s possible, they noted, that individuals with “psychotic dispositions” may self-medicate or show greater disposition to cannabis use.
Moreover, the dataset neither captured important factors regarding the cannabis itself, including delta-9-tetrahydrocannabinol potency, mode of use, product type, or cannabis dependence, nor captured institutionalized and homeless youth.
Nevertheless, they pointed to the findings as supporting a “precautionary principle” — as more jurisdictions move to liberalize cannabis use and perception of harm declines among youth, the findings suggest that evidence-based cannabis prevention strategies for adolescents are warranted.
This study was supported by CAMH, the University of Toronto, and ICES, which is funded by an annual grant from the Ontario Ministry of Health and the Ministry of Long-Term Care. The authors declared no relevant financial relationships.
A version of this article appeared on Medscape.com.