Increases in Cannabis-Related Hospitalizations in Ontario Preceded Legalization of Non-medical Use

Cannabis use has recently increased in North America generally and in Canada specifically, but little is known about hospitalizations for cannabis harms, particularly prior to Canada’s 2018 legalization of non-medical use. Researchers conducted a retrospective, population-based cohort study of all hospitalizations for cannabis harms in Ontario, Canada from 2003–2017, using data from the single-payer Ontario Health Insurance Plan.

  • During the study period, approximately two-thirds of hospitalizations for cannabis harms occurred among men, three-quarters occurred among those aged 15–39 years, and two-thirds occurred among those with a comorbid mood or anxiety disorder.
  • Lower income quintiles experienced higher rates of cannabis- related hospitalization; those in the lowest income quintile had a hospitalization rate that was 2.3 times that of those in the highest income quintile.
  • During the study period, cannabis-related hospitalization rates increased 8% annually.
  • Women aged 15–24 experienced the largest increases in hospitalization rates (12% annually), but increases were not significantly different based on income quintiles.

Comments: This study documented a steady increase in hospitalizations for cannabis harms in Ontario prior to legalization of cannabis for recreational use, illustrating that changing use and norms may precede policy change. Hospitalizations disproportionately affected those with low income and mental health conditions. It will be important to see how trends in hospitalizations differ in the post-legalization period, particularly among vulnerable groups.

Timothy S. Naimi, MD, MPH

Reference: Zygmunt A, Tanuseputro P, Brown C, et al. Changes in rates of hospitalization due to cannabis harms in Ontario, Canada before the legalization of nonmedical cannabis: retrospective population-level study between 2003 and 2017. J Addict Med. 2021 [Epub ahead of print]. doi: 10.1097/ADM.0000000000000906

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