High-intensity cannabis use is associated with retention in opioid agonist treatment
Greater retention during treatment for opiate use disorder (OUD) reduces morbidity and mortality and predicts better outcomes. According to preclinical and clinical data, both tetrahydrocannabinol (THC) and cannabidiol (CBD) might reduce opioid withdrawal and pain. CBD is safe in humans and might reduce anxiety and craving for opioids. However, results have been mixed in several large observational studies of the relationship between cannabis use and OUD treatment retention. In another observational study, researchers followed 820 Canadian patients with OUD for a median of 81 months after initiation of opioid replacement therapy (methadone, 99%).
At baseline, daily heroin injections were reported by 44%, daily prescription opioids by 8%, and cannabis use by 49% (17% used cannabis daily). In two semiannual follow-ups, daily use (but not less than daily) was associated with a 20% greater odds of 6-month treatment retention than no cannabis use. Various analyses yielded similar results.
Despite these provocative findings, providers should not recommend cannabis to patients with OUD for several reasons: Of several large observational studies, this is the only one supporting a benefit for retention with cannabis use; in two others, cannabis users had worse outcomes. As an observational study, it may have unmeasured confounders. Cannabis use has several potential associated risks and harms, including psychotic disorder, cognitive impairment, and cannabis use disorder. Finally, the findings might be relevant only to patients on methadone; almost no participant received buprenorphine. That said, cannabis use is unlikely to be excessively detrimental to recovery from OUD. In light of the recent FDA approval of a cannabidiol-containing compound and its classification to Schedule 5, more studies should be performed soon to investigate the utility of CBD for treating substance use disorders.