Cannabis Commercialization, Not Initial Legalization, Was Linked to a 30% Jump in ER Visits for Cannabis-Induced Psychosis

Across 6,300 ER visits for cannabis-induced psychosis, restricted legalization showed no change relative to pre-legalization. Commercialization was associated with an immediate 30% increase (IRR 1.30). The increase was driven by youth above the legal purchase age (19-24, IRR 1.63) but not below it (15-18, IRR 0.73, nonsignificant). No changes were seen in cocaine or methamphetamine psychosis ER visits, serving as negative controls.

Population-based study using health administrative data for all ER visits in Ontario, Canada (population 14.3 million) across three periods: pre-legalization (Jan 2014-Sep 2018), legalization with restrictions (Oct 2018-Feb 2020), and commercialization (Mar 2020-Sep 2021). Segmented regression with cocaine and methamphetamine psychosis as controls.

This study provides a nuanced message: it is not legalization per se that may increase psychosis risk, but rather the commercial expansion phase with more retail stores, more product types, and likely more potent products. The finding that youth above but not below legal purchase age drove the increase suggests retail access matters.

This is a key finding for jurisdictions designing legalization frameworks. Restricting retail outlets and product types during early legalization may serve as a protective buffer. The jump during commercialization aligns with research on how increased product availability and potency can drive harm.

The commercialization period overlapped with COVID-19, which may have independently affected substance use and mental health. Cannot determine whether potency changes, increased access, or other factors drove the increase. Relies on ER diagnostic coding.