Daily cannabis use associated with 50% lower odds of daily illicit opioid use among people with chronic pain | Research

The takeaway

Among people who use drugs and report chronic pain, daily cannabis use was independently associated with half the odds of daily illicit opioid use over a 3.5-year period.

Harm reduction workers, addiction medicine clinicians, policymakers, and chronic pain patients.

OR 0.50 for daily opioid use

What the researchers found

After adjusting for demographics, substance use, and health factors, daily cannabis use was associated with significantly lower odds of daily illicit opioid use (adjusted OR 0.50, 95% CI 0.34-0.74, p < 0.001). The most common therapeutic reasons for cannabis use were pain (36%), sleep (35%), stress (31%), and nausea (30%).

Why it matters

This is rare individual-level longitudinal data supporting the population-level finding that cannabis access may reduce opioid use. Most prior evidence was ecological (state-level), making individual associations difficult to establish.

The numbers in context

1,152 participants; 40% reported daily illicit opioid use; 36% reported daily cannabis use; adjusted OR 0.50 (95% CI 0.34-0.74); median age 49.3 years; 36.8% women.

How the study worked

Longitudinal analysis of 1,152 people who use drugs with chronic pain from two prospective Vancouver cohorts (June 2014-December 2017), using generalized linear mixed-effects models with 6-month follow-up periods.

What this study cannot tell us

Self-reported substance use and pain. Population is people who already use drugs, not representative of all chronic pain patients. No data on cannabis preparations, dosages, or administration methods. Observational design cannot prove causation.

How to read the evidence

Moderate: longitudinal cohort with adjusted analysis, but observational design and specific population.

When this study was published

Published in 2019.

The bigger picture

While ecological studies have shown lower opioid overdose rates in medical cannabis states, individual-level data has been largely missing. This study fills that gap, though it involves a specific population (people who already use drugs) rather than the general public.

Questions still open

Does this substitution effect hold for people who are not already using illicit drugs? What cannabis preparations and doses are most effective for opioid substitution?

Common questions

Does cannabis replace opioids for pain?

In this study of people who use drugs with chronic pain, daily cannabis users had half the odds of daily illicit opioid use, but the study cannot prove cannabis caused the reduction.

Why did participants use cannabis?

The most common reasons were pain (36%), sleep (35%), stress (31%), and nausea (30%).

Read the original research

Frequency of cannabis and illicit opioid use among people who use drugs and report chronic pain: A longitudinal analysis.

PLoS medicine, 16(11), e1002967

View on PubMed ↗Publisher’s paper ↗

Citation

Lake, Stephanie; Walsh, Zach; Kerr, Thomas; Cooper, Ziva D; Buxton, Jane; Wood, Evan; Ware, Mark A; Milloy, M J. (2019). Frequency of cannabis and illicit opioid use among people who use drugs and report chronic pain: A longitudinal analysis.. PLoS medicine, 16(11), e1002967. https://doi.org/10.1371/journal.pmed.1002967