Cannabis Use Was Associated With Lower Self-Reported Opioid Use in a Vancouver Study
A 2023 study of people using unregulated opioids in Vancouver found that those who used cannabis to manage opioid cravings were more likely to report reducing their opioid use. The finding points to a possible harm-reduction role for cannabis, but it does not establish that cannabis causes people to use fewer opioids or that it can replace evidence-based treatment for opioid use disorder.
The study, published in the International Journal of Drug Policy, analyzed questionnaire data from 205 people who used both cannabis and unregulated opioids. Participants were recruited between December 2019 and November 2021 through research cohorts in Vancouver, Canada.
Researchers asked participants why they used cannabis and whether their opioid use changed during periods when they used cannabis. In the study’s primary analysis, cannabis use to manage opioid cravings was associated with higher odds of self-reported reductions in opioid use. The adjusted odds ratio was 2.13, with a 95% confidence interval of 1.07 to 4.27.
The association was stronger in some subgroups. Among participants living with moderate to severe pain, cannabis use to manage cravings was associated with an adjusted odds ratio of 4.44 for reporting reduced opioid use. The association was also observed among female participants, although the subgroup estimates were based on smaller numbers and were therefore less precise.
These findings are relevant to the risks of the unregulated drug supply. Illegally manufactured fentanyl is commonly found in powders and counterfeit pills, and people may not know what substances their drugs contain. The Centers for Disease Control and Prevention’s overview of fentanyl explains why unexpected exposure can substantially increase overdose risk.
However, the study has important limitations. It was cross-sectional, relied on participants’ self-reports, and measured an association rather than a cause-and-effect relationship. The researchers did not randomly assign people to use cannabis, verify the contents or doses of cannabis products, or determine whether cannabis reduced overdose risk. People who used cannabis and reduced their opioid use may also have differed from other participants in ways the analysis could not fully capture.
The authors concluded that improving access to cannabis products for therapeutic use might be a useful supplementary harm-reduction strategy during the drug-toxicity crisis. That conclusion is more limited than suggesting that legal cannabis is a proven or safer substitute for opioids. Cannabis itself can cause adverse effects, including impairment, dizziness, and sleepiness, and evidence for reducing opioid use remains mixed. The National Center for Complementary and Integrative Health’s review of cannabis research notes that studies examining cannabis alongside opioids have produced inconsistent results.
For people with opioid use disorder, cannabis should not be presented as a replacement for established care. Medications such as methadone, buprenorphine, and naltrexone are supported treatments; guidance summarized by the National Institute on Drug Abuse describes medication treatment as an effective way to reduce illicit opioid use and overdose risk. Other harm-reduction measures, including naloxone, drug checking where available, and avoiding use alone, remain important.
The Vancouver study adds to evidence that some people use cannabis to manage cravings, pain, or withdrawal-related symptoms while reducing their opioid use. Its results justify further research, particularly controlled studies that can assess which cannabis products, if any, are helpful and how their potential benefits compare with their risks.
