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

To characterize the prevalence and reasons for the use of cannabis as a strategy to reduce the harms arising from other substances. We drew data about recent cannabis use and intentions from 3 prospective cohort studies of marginalized people who use drugs based in Vancouver, Canada, from June 2016 to May 2018. The primary outcome was "use of cannabis for harm reduction," defined as using cannabis for substitution for licit or illicit substances such as heroin or other opioids, cocaine, methamphetamine, or alcohol; treating withdrawal; or coming down off other drugs. Approximately 1 in 4 participants reported using cannabis for harm reduction at least once during the study period. The most frequent reasons included substituting for stimulants (50%) and substituting for illicit opioids (31%). The use of cannabis for harm reduction is a common strategy among people who use drugs in our setting. Further research into the factors associated with this strategy is needed. Better characterization of the risks and benefits of substitution strategies, including for opioids and stimulants, may prompt new treatment options for PWUD.