One in four high-risk drug users in Vancouver reported using cannabis to reduce harm from other substances | Research

The takeaway

Among marginalized people who use drugs in Vancouver, approximately 25% reported using cannabis as a harm reduction strategy at least once during the study period, most commonly to substitute for stimulants (50%) and illicit opioids (31%).

Harm reduction advocates, addiction medicine specialists, drug policy researchers, and public health professionals.

25% used cannabis for harm reduction; 50% to substitute for stimulants

What the researchers found

About 1 in 4 participants used cannabis for harm reduction during the study period. The most common reasons were substituting for stimulants (50%) and substituting for illicit opioids (31%). Other reasons included treating withdrawal and coming down off other drugs.

Why it matters

During an overdose crisis that has killed thousands in British Columbia, understanding how people at highest risk are already using cannabis to manage their drug use provides ground-level data that could inform future harm reduction interventions.

The numbers in context

~25% reported cannabis for harm reduction at least once; 50% for stimulant substitution; 31% for opioid substitution; study period June 2016 to May 2018

How the study worked

Data drawn from three prospective cohort studies of marginalized people who use drugs in Vancouver, Canada, from June 2016 to May 2018. Participants reported recent cannabis use and their intentions for using cannabis, including substitution for other substances.

What this study cannot tell us

Self-reported data from marginalized populations in one Canadian city. No comparison group. Cannot determine whether cannabis substitution actually reduced harm. Potential selection bias.

How to read the evidence

Prospective cohort data from three established studies, but self-reported outcomes and single-city setting limit conclusions.

When this study was published

Published in 2021 using data from 2016-2018.

The bigger picture

People who use drugs are already employing cannabis as a self-directed harm reduction tool. Whether this strategy actually reduces overdose risk and other harms remains an important research question with potential implications for drug policy.

Questions still open

Does cannabis substitution actually reduce overdose risk? Would formalized cannabis-based harm reduction programs be effective? What barriers exist to studying cannabis as a harm reduction tool? How do these patterns differ across demographic groups?

Common questions

What substances are people replacing with cannabis?

The most common substitutions were for stimulants (50% of those using cannabis for harm reduction) and illicit opioids (31%). Others used cannabis for treating withdrawal or coming down off other drugs.

Does substituting cannabis for opioids actually prevent overdose?

This study documented the practice but did not measure whether it actually reduced overdose risk. That remains an important unanswered question.

Read the original research

Use of Cannabis for Harm Reduction Among People at High Risk for Overdose in Vancouver, Canada (2016-2018).

American journal of public health, 111(5), 969-972

View on PubMed ↗Publisher’s paper ↗

Citation

Mok, Janice; Milloy, M-J; Grant, Cameron; Lake, Stephanie; DeBeck, Kora; Hayashi, Kanna; Socías, M Eugenia. (2021). Use of Cannabis for Harm Reduction Among People at High Risk for Overdose in Vancouver, Canada (2016-2018).. American journal of public health, 111(5), 969-972. https://doi.org/10.2105/AJPH.2021.306168