Background: Drug decriminalization has been proposed to reduce health and social harms related to illicit substance use. We sought to evaluate changes in outcomes following drug decriminalization and partial recriminalization in British Columbia.

Methods: We obtained data from August 2020 to March 2025 on police-recorded drug incidents nationally from Statistics Canada, opioid- and stimulant-related hospitalizations nationally (excluding Quebec) from the Canadian Institute for Health Information, and drug toxicity deaths in BC, Alberta, and Ontario from provincial, publicly available data sources. We used a controlled interrupted time-series design to compare changes in monthly rates of drug-related hospitalizations and deaths and drug possession incidents between BC and the rest of Canada after decriminalization (February 2023) and subsequent recriminalization (May 2024).

Results: Over the 5-year period, 97 630 drug possession incidents, 161 278 opioid-and 113 747 stimulant-related hospitalizations, and 29 730 drug toxicity deaths occurred in the study regions. In BC, drug possession incidents decreased after decriminalization (incidence rate ratio [IRR] 0.61, 95% confidence interval [CI] 0.42 to 0.86) and increased again after recriminalization (IRR 1.68, 95% CI 1.13 to 2.51), while no significant changes were observed in the rest of Canada. After decriminalization, BC did not differ significantly from other provinces and territories for changes in opioid-related hospitalizations (ratio of rate ratios [RRR] 0.87, 95% CI 0.54 to 1.42), stimulant-related hospitalizations (RRR 0.77, 95% CI 0.50 to 1.28), or deaths from drug toxicity (RRR v. Alberta 0.83, 95% CI 0.64 to 1.06; RRR v. Ontario 1.07, 95% CI 0.64 to 1.78). After recriminalization in BC, changes remained similar to other provinces and territories for opioid-related hospitalizations (RRR 1.03, 95% CI 0.56 to 1.90) and stimulant-related hospitalizations (RRR 1.02, 95% CI 0.59 to 1.76), and similar to Alberta for deaths from drug toxicity (RRR 1.14, 95% CI 0.79 to 1.66).

Interpretation: Drug decriminalization and recriminalization in BC were associated with substantial changes in police-reported drug possession incidents but no corresponding changes in drug toxicity deaths or hospitalizations when compared to other regions in Canada. The findings suggest decriminalization is effective at reducing drug possession incidents but is insufficient in isolation to affect health outcomes.