2025-06-12 –, BS 3.14 - 60 cap.
Background: We sought to evaluate the associations between measures of cannabis use and prevalent risk factors for fatal overdose using longitudinal data gathered from community-recruited structurally-marginalized people who use unregulated drugs (PWUD) in a setting of unprecedented rates of overdose death.
Methods: We used pooled data from three harmonized prospective cohort studies of PWUD in Vancouver, Canada. Generalized estimating equations (GEE) were used to analyze the longitudinal associations between cannabis use, non-fatal overdose, daily unregulated opioid use, and urine fentanyl-positivity.
Results: We included 3,937 PWUD who completed ≥1 study interview between December 2005 to November 2023. In multivariable analyses, ≥daily cannabis use was associated with decreased odds of non-fatal overdose (Adjusted Odds Ratio [AOR]=0.91, 95% confidence interval [CI]: 0.83-0.99) and ≥daily use of unregulated opioids (AOR=0.54, 95% CI: 0.51-0.57). In the multivariable analysis of urine drug screen (UDS) data, tetrahydrocannabinol-positive UDS were associated with decreased odds of non-fatal overdose (AOR=0.82, 95% CI: 0.71-0.94), daily use of unregulated opioids (AOR=0.52, 95% CI: 0.46-0.58) and fentanyl-positive UDS (AOR=0.60, 95% CI: 0.54-0.67).
Conclusions: We observed beneficial associations between measures of cannabis use and risk factors for fatal overdose among community-recruited PWUD. Consistent with mounting preliminary evidence describing how some PWUD at highest risk of overdose use cannabis for harm reduction purposes including substituting for unregulated opioids, these observational findings further support experimentally investigating the risks and possible benefits of controlled administration of legal cannabinoids to reduce the risk of fatal opioid overdose.
Hudson REDDON (a,b), Zach WALSH (a,c), Eric C. Sayre (a), Kora DeBECK (a,d), Kanna HAYASHI (a,e), M-J MILLOY (a,b)
a. British Columbia Centre on Substance Use, Vancouver, BC V6Z 2A9, Canada
b. Department of Medicine, University of British Columbia, Vancouver, BC V6Z 1Y6, Canada
c. University of British Columbia, Department of Psychology, Kelowna, BC, V1V 1V7, Canada
d. School of Public Policy, Simon Fraser University, Burnaby, BC V6B 5K3, Canada
e. Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada.
Hudson Reddon, PhD is a Research Scientist at the BCCSU and Assistant Professor at the University of British Columbia, Faculty of Medicine.
At the BCCSU, Dr. Reddon’s research focus is to conduct innovative longitudinal research to elucidate the risks, as well as the potential benefits, of evolving cannabis use/access patterns among people at highest risk of overdose and other substance-related harms during the fentanyl era. He has an established track record of attracting research funds as a principal investigator or co-applicant (Canadian Institutes of Health Research, Public Health Agency of Canada) and has published numerous peer-reviewed scientific papers in high impact academic journals including Clinical Infectious Diseases, American Journal of Public Health and Lancet HIV. Dr. Reddon has a keen interest in teaching and completed a Bachelors of Education degree at the University of Toronto. He has been involved in the design and delivery of curriculum among undergraduate and graduate students in the areas of health equity and chronic disease management at UBC and Trinity College Dublin. Dr. Reddon holds a Michael Smith Health Research BC Scholar Award and received his graduate training at McMaster University in Health Research Methodology and Clinical Epidemiology. He is an active member of the Canadian Society of Addiction Medicine, the International Cannabinoid Research Society and the Canadian HIV Trials Network.