Frequent cannabis use was linked to 71% fewer opioid overdoses among methadone patients | Research

The takeaway

Among 446 patients in methadone treatment, those who used cannabis frequently had a 71% lower likelihood of reporting a nonfatal opioid overdose in the past year.

Harm reduction advocates, addiction treatment providers, opioid use disorder researchers

71% lower likelihood of nonfatal opioid overdose among frequent cannabis users

What the researchers found

Nonfatal opioid overdose prevalence was 3% among frequent cannabis users vs 9% among infrequent/non-users (p=0.02). After controlling for demographic and clinical factors, frequent cannabis users had 71% lower likelihood of overdose (adjusted RR=0.29, 95% CI 0.10-0.80).

Why it matters

Opioid overdose remains a leading cause of death. If cannabis use genuinely reduces overdose risk among people in treatment for opioid use disorder, it could inform harm reduction strategies.

The numbers in context

446 participants; 35% frequent cannabis users; 7% reported nonfatal overdose; 3% overdose among frequent users vs 9% among infrequent; adjusted RR=0.29 (71% reduction); 95% CI 0.10-0.80

How the study worked

Cross-sectional survey of 446 individuals enrolled in four methadone maintenance treatment clinics in Washington State and southern New England, comparing frequent (weekly+) vs infrequent cannabis users.

What this study cannot tell us

Cross-sectional design cannot establish causation. Self-reported cannabis use and overdose. Convenience sample may not represent all MMT patients. Possible confounders not captured. Reverse causation possible (those at higher overdose risk may avoid cannabis).

How to read the evidence

Cross-sectional survey with significant association but inability to establish causation

When this study was published

Published in 2021. The relationship between cannabis and opioid outcomes remains actively debated.

The bigger picture

This individual-level finding complements ecological studies showing lower overdose rates in states with cannabis laws, providing preliminary evidence that the association may operate at the individual patient level.

Questions still open

Is cannabis providing pain relief that reduces supplemental opioid use? Or does frequent cannabis use identify a subpopulation with different risk factors? Would a prospective study confirm this protective association?

Common questions

Can cannabis reduce opioid overdose risk?

In this study of methadone patients, frequent cannabis users had 71% lower odds of nonfatal overdose. However, the cross-sectional design cannot prove cannabis caused this reduction, and other explanations are possible.

Should opioid treatment programs encourage cannabis use?

The authors caution against causal interpretation. While the association is noteworthy, additional prospective studies are needed before cannabis could be considered part of a harm reduction strategy for opioid use disorder.

Read the original research

Cannabis Use and Nonfatal Opioid Overdose among Patients Enrolled in Methadone Maintenance Treatment.

Substance use & misuse, 56(5), 697-703

View on PubMed ↗Publisher’s paper ↗

Citation

Bryson, William C; Morasco, Benjamin J; Cotton, Brandi P; Thielke, Stephen M. (2021). Cannabis Use and Nonfatal Opioid Overdose among Patients Enrolled in Methadone Maintenance Treatment.. Substance use & misuse, 56(5), 697-703. https://doi.org/10.1080/10826084.2021.1892137