No Association between Cannabis and Non-prescription Opioid Use among People Receiving Medications for Opioid Use Disorder

One of the reasons cited for the legalization of cannabis for medical and non-medical use is that it might decrease unhealthy opioid use through substitution effects. To date, however, evidence on this is mixed, and the co-use of cannabis and opioids is common. Researchers conducted a meta-analysis of longitudinal cohort studies of the relationship between cannabis use and non-medical opioid use among people with opioid use disorder (OUD) receiving medications for OUD (i.e., methadone, buprenorphine, and intramuscular naltrexone); cross sectional and retrospective studies were excluded.

• Ten trials were analyzed; they included 8367 people with OUD; of these, 76 percent, 21 percent, and 2 percent were treated with methadone, buprenorphine, and naltrexone, respectively. The average follow-up time was 9.7 months.
• In the pooled meta-analysis, there was no association between cannabis use and non-medical opioid use (odds ratio, 1.00).
• The lack of association persisted after removal of two trials that were outliers, and a subgroup analysis based on people receiving methadone and buprenorphine only.

Comments: This meta-analysis of longitudinal studies found no association between cannabis and non-medical opioid use among people receiving pharmacologic treatment for OUD. In the context of treatment, clinical trials could better assess relationships between cannabis and non-medical opioid use.

Timothy S. Naimi, MD, MPH

Reference: Costa GP, Nunes JC, Heringer DL, et al. The impact of cannabis on non-medical opioid use among individuals receiving pharmacotherapies for opioid use disorder: a systematic review and meta-analysis of longitudinal studies. Am J Drug Alcohol Abuse. 2024;50(1):12–26.