People with chronic pain who use cannabis daily are far less likely to use illicit opioids, including fentanyl, a University of B.C. study shows.

The findings, based on self-reports over three years by 1,152 people about their drug use and pain, suggest cannabis might serve as a proxy for illicit opioids. The researchers did the study among marginalized residents of the Downtown Eastside, some of them injection drug users, to see if cannabis might be a potential alternative for opioids in a neighbourhood that’s been hit hard by the overdose epidemic.

The findings were reported in the publication PLOS Medicine.

Daily cannabis users were half as likely to use illicit street opioids for chronic pain and sleep problems as non-users of cannabis, according to researchers from UBC and the British Columbia Centre on Substance Use.

The results are a stark contrast to another recent study by researchers at McMaster University who found that cannabis was not of any help in reducing opioid use among those getting addiction treatment. The researchers did a meta-analysis of studies involving individuals using methadone maintenance therapy for opioid use disorder and they concluded that cannabis didn’t reduce opioid use. That study is published in the Canadian Medical Association Open journal.

Dr. Zena Samaan, the lead author, said in an email that the B.C. study is not a direct comparison as it included fewer than a third of the subjects as the McMaster study and used self-reporting. Still, “we found no evidence to suggest cannabis helps patients with opioid use disorder stop using opioids.”

“Previous work on primary data from Canada showed cannabis use increased opioid use in women and that cannabis users (men and women) continue to use opioids despite being in treatment. More recent studies from the U.S.A. showed that in the states where cannabis is medically available, the opioid-related deaths are higher,” said Samaan, an associate professor of psychiatry and behavioural neurosciences.

She poured more cold water on the B.C. findings, saying she is somewhat wary of the B.C. study because one of the authors, M-J Milloy, is “supported by a cannabis company” which may bias the study.

Milloy, who is the Canopy Growth professor of cannabis science at UBC, said he gets no research funding from any cannabis industry groups “nor do I have any financial relationship with the cannabis industry.”

The Canopy professorship was established with a $2.5 million donation to UBC and the Centre for Substance Abuse to help fund research “aimed at defining the potential benefits of cannabis as a legitimate therapeutic treatment for opioid use disorder” according to a statement from the company.

Milloy said the funding for his professorship comes from arms’ length gifts to UBC from Canopy Growth, a licensed producer of cannabis, along with the B.C. Ministry of Mental Health and Addictions.

“As a UBC faculty member, I enjoy all of the institution’s many protections of my academic freedom and comply with all of their requirements around academic integrity, including annual reviews of any conflicts of interest and full peer review of my research studies. Quite simply, Canopy (nor any other industry group) has no influence over the work I do or the results I publish.”

The study he co-wrote was funded by grants to UBC from the U.S. National Institute on Drug Abuse, he said, not any industry group.

Milloy said the latest study shows that in some cases, people are using cannabis instead of illicit opioids. And with the fentanyl crisis causing so many overdose deaths, the results suggest that “increasing access to cannabis might help curb overdoses.”

Future research will delve into whether or not cannabis can help people diagnosed with opioid addiction stay on treatment and if cannabis can be a substitute for opioid use.

Meanwhile, Vancouver Coastal Health has launched a unique pilot program in the Downtown Eastside that offers physiotherapy, individual and group counselling and other interventions to help people manage pain without opioids or any pain medications.

Judy Darcy, Minister of Mental Health and Addictions, has said there’s no “one size fits all” approach in the path to healing” so the DTES Chronic Pain Service was launched earlier this year to serve clients of Vancouver Community Primary Care. It has already hit its limit of 200 appointments a month.

The program includes a class series called Making Sense of Pain, which was developed by Pain B.C., a registered charity supporting people with chronic pain.