Cannabis reduces long term opioid use no evidence found

A 20-year Australian study has found no evidence to suggest cannabis reduces illicit opioid use, and it may not be an effective long-term method of reducing harm for those with an opioid use disorder or problematic use of opioids.

Published in the American Journal of Psychiatry, the University of Sydney led study is one of the longest of its kind. Between 2001 to 2022, the study involved a group of 615 people with heroin dependence, many of whom also used cannabis.

Opioid use is currently responsible for more death and disability than any other illicit drug. Opioid and cannabis use disorders make up approximately 77 percent of all illicit drug disorders. The researchers say clinicians and policymakers should be cautious about relying on cannabis to reduce problematic opioid use or as a potential strategy to help manage the opioid crisis, especially given a global shift towards cannabis legalisation and recognition as a therapeutic product.

To examine the impact of cannabis on opioid use, and vice versa, researchers used a recently developed statistical technique. This allowed them to account for influential factors on opioid and cannabis use in the data such as age and made it possible to focus on individual changes in substance use over time.

“Our investigation shows that cannabis use remains common among this population, but it may not be an effective long term strategy for reducing opioid use ,” says lead author Dr Jack Wilson, from The Matilda Centre for Research in Mental Health and Substance Use, at the University of Sydney.

Reference: The long-term relationship between cannabis and heroin use: An 18-20-year follow-up of the Australian Treatment Outcome Study (ATOS); American Journal of Psychiatry