Does cannabis use during opioid addiction treatment affect outcomes? Review of 41 studies says mostly not | Research

The takeaway

A systematic review of 41 studies found that cannabis use during medication-based opioid addiction treatment was mostly unrelated to treatment outcomes like opioid use, adherence, and retention.

Addiction medicine clinicians, opioid treatment program administrators, and harm reduction advocates.

41 studies: majority found no link between cannabis use and opioid treatment outcomes

What the researchers found

Across 41 studies examining cannabis use during methadone, buprenorphine, or naltrexone treatment for opioid use disorder, the majority found no significant association between cannabis use and opioid use, treatment adherence, or retention. A small number of studies found either supportive or detrimental effects, but these were inconsistent.

Why it matters

Clinicians often worry that cannabis use might undermine opioid addiction treatment. This comprehensive review suggests those concerns are largely unsupported by evidence, which could influence how treatment programs handle cannabis-positive patients.

The numbers in context

41 studies included (23 methadone, 7 buprenorphine, 6 naltrexone, 5 mixed); majority found no significant association between cannabis use and primary outcomes.

How the study worked

Systematic review of 41 peer-reviewed studies across seven databases examining cannabis use during medication-based opioid use disorder treatment (methadone, buprenorphine, naltrexone).

What this study cannot tell us

High heterogeneity in how cannabis use was measured and defined across studies; most studies were observational; potential confounding from polysubstance use; cannabis use patterns varied widely.

How to read the evidence

Moderate: systematic review of 41 studies with consistent findings, though limited by observational designs and heterogeneous cannabis measures.

When this study was published

Published 2020.

The bigger picture

Some researchers have proposed that cannabis could help manage opioid cravings and withdrawal. While this review does not confirm that hypothesis, the absence of consistent harm suggests cannabis use should not automatically disqualify patients from opioid treatment programs.

Questions still open

Could intentional cannabis use (rather than incidental) during opioid treatment actually improve craving and withdrawal outcomes? Should treatment programs reconsider punitive policies for cannabis-positive patients?

Common questions

Does cannabis use hurt opioid addiction treatment outcomes?

The majority of 41 studies found no significant association between cannabis use and opioid treatment outcomes. A few studies found either positive or negative effects, but these were inconsistent.

Should opioid treatment programs ban cannabis use?

The evidence does not support the idea that cannabis use independently threatens treatment outcomes, suggesting punitive approaches to cannabis-positive patients may not be justified.

Read the original research

The relationship between cannabis use and patient outcomes in medication-based treatment of opioid use disorder: A systematic review.

Clinical psychology review, 82, 101939

View on PubMed ↗Publisher’s paper ↗

Citation

Lake, Stephanie; St Pierre, Michelle. (2020). The relationship between cannabis use and patient outcomes in medication-based treatment of opioid use disorder: A systematic review.. Clinical psychology review, 82, 101939. https://doi.org/10.1016/j.cpr.2020.101939