The impact of drug decriminalization policy on mental health- and substance-related service utilization among people who use drugs with prior care in British Columbia

Background In 2023, British Columbia implemented a pilot illicit drug decriminalization policy aimed at addressing the high burden of illicit drug toxicity deaths, creating a need to examine its health system impacts. Although research on decriminalization has largely focused only on substance-related outcomes, broader mental health service utilization, including substance-related mental health care, among people who use drugs remains an insufficiently studied domain that this study seeks to address. Methods In this single interrupted time series analysis of prevalent people who use drugs with prior care (PWUD-PC) in BC, we examined the proportion of people who accessed mental health and substance-related (MH-SR) services and their average monthly MH-SR visits one year before and after the decriminalization policy, stratified by physician visits, emergency department visits, and hospitalizations. Results The population prevalence of PWUD-PC remained stable at 1.8% before and after decriminalization, and no statistically significant changes were observed in the proportion of PWUD-PC accessing MH-SR physician services and hospitalizations. The early period following decriminalization did not produce large shifts in overall MH-SR service use among PWUD-PC. Some movements in trends were seen in emergency department use, while several other outcomes, particularly in hospitalizations and physician visits, continued pre-existing trends. Conclusion Overall, we found stable patterns of MH-SR service engagement across the intervention period and small shifts in the post-intervention trends of average MH-SR service visits. These findings suggest that the early period following decriminalization did not lead to abrupt or large shifts in MH-SR service use among PWUD-PC.