Friday, February 23, 2018 - 10:45

Claims that medical cannabis use has reduced opioid overdose deaths in the United States have been challenged by a University of Queensland drug abuse expert.

Professor Wayne Hall from UQ’s Centre for Youth Substance Abuse Research said there was weak evidence to support the claims.

“The statements that legalising medical marijuana reduces opioid overdose deaths by offering a less risky method of pain management are based on studies with results that have not been confirmed through more rigorous scientific methods,” Professor Hall said.

“Although the studies show a relationship over time between the passing of medical marijuana laws and the reduction of opioid overdose death rates, they do not provide good evidence that the laws caused the reduction in deaths.”

Professor Hall said there were more plausible reasons for the reduction in opioid deaths that should be investigated.

“Politically conservative American states are less likely to pass medical cannabis laws, less likely to provide treatment programs for opioid dependence, and more likely to use imprisonment instead,” he said.

“Access to medically assisted treatment programs for opioid dependence, such as methadone and buprenorphine, is known to reduce overdose risk.

“Similarly, the risk of overdose death for opioid users increases dramatically after they leave prison.”

Professor Hall also urged caution of the premature acceptance of research claiming the pain relief qualities of medical cannabis.

“A recent review found that the analgesic effect of cannabinoids was modest, at best,” he said.

“An Australian study found that chronic pain patients who used cannabis did not use lower doses of opioids or report less pain than those who did not.

“The rush to prematurely draw conclusions about the effects of medical cannabis risk is detracting attention from proven methods of reducing opioid overdose deaths.”

Professor Hall’s full commentary is published in the journal Addiction.

Media: Professor Wayne Hall, w.hall@uq.edu.au, +61 7 3365 5246; Dani Nash, UQ Communications, dani.nash@uq.edu.au , +61 7 3346 3035.