A study set to publish in the journal, Applied Health Economics and Health Policy, has found that legalizing cannabis has led to a “marked decline” in the volume of opioids prescribed across Canada.

Nearly 18,000 Canadians died from an opioid-related overdose from January 2016 to June 2020, according to the federal Public Health Infobase.

“Our findings support the hypothesis that easier access to cannabis for pain may reduce opioid use for both public and private drug plans,” notes the study abstract.

Working with national prescription claims data from private and public payers between January 2016 and June 2019, the study tracked total opioid prescribing volumes and expenditures prior to and following cannabis legalization.

Researchers took into account morphine, codeine, fentanyl, hydrocodone, hydromorphone, meperidine, oxycodone, tramadol and the non-opioids gabapentin and pregabalin, which were analyzed separately from the opioids. All opioid volumes were converted to a mean morphine equivalent dose.

The study found that, following legalization, total monthly opioid spending by public payers fell from $267,000 per month to $95,000, and that the average dose also declined from 22.3 milligrams per claim to 4.1 mg.

In a blog post, the National Organization for the Reform of Marijuana Laws notes that the findings are in line with previous studies that have found that cannabis access is associated with declines in overall prescription drug activity.

A 2020 study published in the Journal of Health Economics found that increasing access to low-THC, high-CBD products in Italy led to significant decreases in the number of dispensed anxiolytics, sedatives and anti-psychotics.