No Current Credible Evidence Cannabis Use is Helpful in Opioid Addiction What are the main findings?

Response: The study main findings include using systematic review methods and including 3676 patients,  cannabis use was not associated with any change in opioid use pattern or treatment retention in patients with opioid use disorder receiving methadone maintenance treatment. There was a significant heterogeneity among the included studies with several methodological limitations calling for better quality studies to be conducted. What should readers take away from your report?

Response: The key message is that the evidence related to cannabis use as a replacement for opioid is poor and fraught with many challenges, the best attempt at compiling all available published literature to reach a consensus on the utility of cannabis in opioid addiction falls short of confirming or denying the benefits or harms of cannabis in the context of opioid use due to the limitations stated earlier. Nonetheless this work is the best available, unbiased summary of what is currently available on the issue of cannabis and opioids.

The conclusion is that there is no current credible and reproducible evidence that cannabis use is helpful in opioid addiction and caution is advised when considering cannabis in patients with opioid use disorder. What recommendations do you have for future research as a result of this work?

Response: Future studies should include a systematic assessment of cannabis use in this population to include types, amount, pattern, route of administration, reasons for use (for example comorbid pain conditions), measures of cannabis use disorder, any co substance use and prospective study design.

The authors have no conflict of interest to disclose, our research is supported by research grants from the Canadian Institutes of Health Research.


Heather McBrien, Candice Luo, Nitika Sanger, Laura Zielinski, Meha Bhatt, Xi Ming Zhu, David C. Marsh, Lehana Thabane, and Zainab Samaan

Cannabis use during methadone maintenance treatment for opioid use disorder: a systematic review and meta-analysis
cmajo 7:E665-E673; published online November 19, 2019, doi:10.9778/cmajo.20190026

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