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Study breakdown

One in five people who use illicit opioids intentionally substitute other substances, with cannabis being common

Longitudinal CohortModerate evidence
The takeaway

Among 1,527 people who use drugs in Vancouver, 22% reported intentionally using another substance to reduce opioid use, with stimulants (50%) and cannabis (28%) being the most common substitutes.

Harm reduction workers, addiction medicine clinicians, and policymakers evaluating cannabis as an opioid substitute.

22% intentionally substituted; cannabis used by 28% of substituters

What the researchers found

22% of illicit opioid users reported substituting at least once during the study. Substitutes used: stimulants (50.3%), cannabis (27.6%), alcohol (3.2%), benzodiazepines (4.5%), and others (4.3%). Daily cannabis use was positively associated with reporting substitution attempts (AOR 1.56, 95% CI 1.24-1.96).

Why it matters

Understanding drug substitution patterns is critical as harm reduction strategies evolve. The finding that cannabis is the second most common intentional opioid substitute suggests it may play a role in informal self-managed opioid reduction.

The numbers in context

1,527 participants, 4,991 interviews. 336 (22%) reported substitution at least once (467 interviews, 9.4%). Cannabis substitution: 129 (27.6%). Stimulant substitution: 235 (50.3%). Daily cannabis use AOR: 1.56 for substitution attempts.

How the study worked

Analysis of three prospective cohorts of people who use drugs in Vancouver, Canada (June 2012 to June 2016). 1,527 participants contributed 4,991 interviews. Multivariable generalized estimating equations examined correlates of intentional substitution.

What this study cannot tell us

Observational design cannot determine whether substitution actually reduced opioid use. Vancouver drug-using population may not generalize. Self-reported substitution intentions. Stimulant substitution being most common raises safety concerns of its own.

How to read the evidence

Large prospective cohort with repeated measures, but cannot establish whether substitution effectively reduced opioid use.

When this study was published

Published in 2022, covering June 2012 to June 2016.

The bigger picture

Drug substitution is a widespread but understudied phenomenon. If people who use opioids are already using cannabis as a harm reduction strategy, formal research into whether this works could inform policy.

Questions still open

  • Does cannabis substitution actually reduce opioid use long-term? Are people substituting stimulants at higher risk of other harms? Should harm reduction programs formally incorporate substitution strategies?

Common questions

Do people use cannabis to get off opioids?
In this Vancouver study, 28% of people who intentionally substituted substances to reduce opioid use chose cannabis, making it the second most common substitute after stimulants.
Does substituting cannabis for opioids work?
This study found that daily cannabis use was associated with substitution attempts, but could not determine whether substitution actually reduced opioid use or improved outcomes.

Read the original research

Prevalence and correlates of intentional substance use to reduce illicit opioid use in a Canadian setting.

Journal of substance use, 27(3), 277-282

Citation

Klimas, Jan; Mok, Wing Yin; Lake, Stephanie; Eugenia Socías, M; DeBeck, Kora; Hayashi, Kanna; Wood, Evan; Milloy, M-J. (2022). Prevalence and correlates of intentional substance use to reduce illicit opioid use in a Canadian setting.. Journal of substance use, 27(3), 277-282. https://doi.org/10.1080/14659891.2021.1941341

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