Daily cannabis use was associated with 26% faster cessation of opioid injection in people who inject drugs | Research

The takeaway

In a 13-year prospective study of people who inject drugs in Vancouver, daily cannabis use was associated with 26% faster cessation of opioid injection specifically, without increasing injection relapse risk.

Addiction medicine specialists, harm reduction workers, and opioid crisis policymakers.

26% faster opioid injection cessation with daily cannabis use

What the researchers found

Among three prospective cohorts of people who inject drugs (PWID) in Vancouver from 2005-2018, at-least-daily cannabis use was associated with 16% faster injection cessation overall (AHR 1.16, CI 1.03-1.30). The effect was driven entirely by opioid injection cessation (AHR 1.26, CI 1.12-1.41), with no significant association for other drug injection cessation. Daily cannabis use was not associated with injection relapse (AHR 1.08, CI 0.95-1.23).

Why it matters

During an ongoing opioid overdose crisis, any intervention that helps people stop injecting opioids is significant. The opioid-specific effect (not general injection cessation) suggests cannabis may address something unique about opioid dependence.

The numbers in context

13-year follow-up (2005-2018); daily cannabis: 16% faster injection cessation overall (AHR 1.16); 26% faster opioid injection cessation specifically (AHR 1.26); no significant injection relapse risk (AHR 1.08).

How the study worked

Extended Cox regression analysis with time-updated covariates from three prospective cohorts of PWID in Vancouver, Canada (2005-2018), examining associations between cannabis use frequency and injection cessation and relapse.

What this study cannot tell us

Observational (cannot establish causation); self-reported cannabis use and injection behavior; unmeasured confounders possible; Vancouver-specific harm reduction context may not generalize; cannot determine cannabis dose, potency, or route.

How to read the evidence

Strong: large prospective design over 13 years with time-updated analysis and appropriate adjustments.

When this study was published

Published 2020.

The bigger picture

This adds to a growing body of evidence suggesting cannabis may serve as an "exit drug" from opioids rather than a "gateway drug" to harder substances. The opioid-specific effect strengthens this argument.

Questions still open

Would structured medical cannabis programs help people who inject opioids transition to safer patterns? What mechanism explains the opioid-specific effect?

Common questions

Can cannabis help people stop injecting opioids?

In this 13-year study, daily cannabis use was associated with 26% faster cessation of opioid injection in people who inject drugs, without increasing relapse risk. However, this is observational and cannot prove cannabis caused the cessation.

Is cannabis a "gateway" or "exit" drug for opioids?

This study supports the "exit drug" hypothesis. Daily cannabis was associated with faster opioid injection cessation specifically, while not increasing the risk of returning to injection drug use.

Read the original research

Frequent Cannabis Use and Cessation of Injection of Opioids, Vancouver, Canada, 2005-2018.

American journal of public health, 110(10), 1553-1560

View on PubMed ↗Publisher’s paper ↗

Citation

Reddon, Hudson; DeBeck, Kora; Socias, M Eugenia; Lake, Stephanie; Dong, Huiru; Karamouzian, Mohammad; Hayashi, Kanna; Kerr, Thomas; Milloy, M-J. (2020). Frequent Cannabis Use and Cessation of Injection of Opioids, Vancouver, Canada, 2005-2018.. American journal of public health, 110(10), 1553-1560. https://doi.org/10.2105/AJPH.2020.305825