Daily Cannabis Use Was Linked to Better Retention in Opioid Treatment Programs | Research

The takeaway

People who used cannabis daily had 21% greater odds of staying in opioid agonist treatment (methadone or buprenorphine) compared to less-than-daily users, in a large cohort followed for nearly 7 years.

Addiction medicine providers, opioid treatment program directors, harm reduction advocates.

Daily cannabis use was associated with 21% greater odds of retention in opioid treatment (aOR 1.21, 95% CI 1.04-1.41).

What the researchers found

Daily cannabis use was positively associated with retention in OAT (adjusted OR 1.21, 95% CI 1.04-1.41). Compared to non-users, daily users had increased odds of retention (aOR 1.20, 95% CI 1.02-1.43), but less-than-daily users did not (aOR 1.00, 95% CI 0.87-1.14), suggesting a dose-response relationship.

Why it matters

Retention in opioid agonist treatment is the single strongest predictor of reduced opioid-related morbidity and mortality. If daily cannabis use supports treatment retention, it could be an important harm reduction consideration during the opioid crisis.

The numbers in context

820 participants, 57.8% men, 32.2% HIV-positive. Median follow-up 81 months. Daily cannabis use: aOR 1.21 (95% CI 1.04-1.41) for treatment retention. Less-than-daily use showed no association.

How the study worked

Longitudinal analysis of 820 participants from two community-recruited prospective cohorts of people who use illicit drugs in Vancouver, Canada. Followed for a median of 81 months with 6-month assessment periods.

What this study cannot tell us

Observational study cannot prove causation. Self-reported cannabis use. Vancouver population may not generalize. Unmeasured confounders possible. Cannot determine why cannabis use might support retention.

How to read the evidence

Moderate - large prospective cohort with long follow-up and appropriate adjustments, but observational.

When this study was published

Published in 2018. Data collected 1996-2016 in Vancouver.

The bigger picture

While some treatment providers worry about cannabis use during opioid treatment, this study suggests daily cannabis use may actually support treatment engagement. This challenges policies that penalize cannabis use in opioid treatment programs.

Questions still open

What mechanism explains the association - does cannabis reduce withdrawal symptoms, cravings, or anxiety? Should opioid treatment programs adopt more permissive cannabis policies? Would this finding replicate in randomized trials?

Common questions

Does cannabis use help people stay in opioid treatment?

This large study found daily cannabis users had 21% greater odds of remaining in opioid agonist treatment. Interestingly, less-than-daily use showed no benefit, suggesting only regular cannabis use was associated with improved retention.

Should opioid treatment programs allow cannabis use?

This study suggests daily cannabis use during opioid treatment may support retention rather than hinder it. Since treatment retention is the strongest predictor of reduced opioid-related death, policies that penalize cannabis use in these programs may need reconsideration.

Read the original research

High-intensity cannabis use is associated with retention in opioid agonist treatment: a longitudinal analysis.

Addiction (Abingdon, England), 113(12), 2250-2258

View on PubMed ↗Publisher’s paper ↗

Citation

Socías, Maria Eugenia; Wood, Evan; Lake, Stephanie; Nolan, Seonaid; Fairbairn, Nadia; Hayashi, Kanna; Shulha, Hennady P; Liu, Seagle; Kerr, Thomas; Milloy, M-J. (2018). High-intensity cannabis use is associated with retention in opioid agonist treatment: a longitudinal analysis.. Addiction (Abingdon, England), 113(12), 2250-2258. https://doi.org/10.1111/add.14398