An Australian study – one of the longest of its type – suggests there is no evidence cannabis reduces long term opioid use among those with an opioid use disorder.
As opioid abuse – prescribed and illicit – continues to wreak havoc in communities, there have been some studies indicating cannabis could help address the opioid epidemic. In the USA, some jurisdictions allow for cannabis to be prescribed in lieu of opioids, or to help/treat opioid use disorder.
“There are claims that cannabis may help decrease opioid use or help people with opioid use disorders keep up with treatment,” said lead author Dr Jack Wilson from The Matilda Centre for Research in Mental Health and Substance Use at the University of Sydney. “But it’s crucial to note those studies examine short- term impact, and focus on treatment of chronic pain and pain management, rather than levels of opioid use in other contexts.”
To examine the impact of cannabis on opioid use (and vice versa) and overcome limitations identified in previous longitudinal studies, the University of Sydney led study used a recently developed statistical technique with a group of 615 heroin-dependent people between 2001 to 2022. Many of the group also used cannabis.
After baseline interviews, participants were reinterviewed at 3, 12, 24, and 36 months, and at 11 and 18–20 years. A couple of the significant findings from the study:
- An increase in cannabis use 24 months after baseline was significantly associated with an increase in heroin use at 36 months.
- An increase in heroin use at 3 months and 24 months was significantly associated with a decrease in cannabis use at 12 months and 36 months.
Among the researchers’ conclusions:
“Overall, there was insufficient evidence to suggest a unidirectional or bidirectional relationship between the use of these substances.”
It’s important to note that the study only involved heroin users, but additional analysis also found no consistent evidence between cannabis and other opioid use, including those that were prescribed.
The study has been published in the American Journal of Psychiatry.