Cannabis Legalization Linked to Reduced Opioid Use, McGill Study Finds

Opioid Prescription Rates Declined in Legal States

States that legalized adult-use cannabis saw prescription opioid dispensing rates drop by an average of 6.9 percent within two years of implementation, according to the McGill analysis. Researchers at McGill's Faculty of Medicine and Health Sciences examined Medicaid and Medicare Part D prescription data from 2010 through 2024 across all 50 states. States with operational retail markets showed the steepest declines. Medical-only programs produced smaller but still measurable reductions.

The research controlled for pre-existing trends in opioid prescribing, state-level demographic variables, and concurrent policy changes including prescription drug monitoring programs. Lead author Dr. Émilie Fortier noted the effect was most pronounced for chronic pain patients under age 65.

Overdose Deaths Also Fell Post-Legalization

Opioid-involved overdose deaths declined by 4.2 percent on average in states with adult-use legalization, the study found. Prescription opioids and heroin drove the reduction, while fentanyl-involved deaths showed no statistically significant change. McGill's team used CDC WONDER mortality data and state-level toxicology reports to isolate cannabis policy effects from broader trends in the overdose crisis.

Earlier research from RAND Corporation and the University of Kentucky documented similar substitution patterns. For full background on this story, see the CannIntel topic hub on cannabis legalization health impacts.

Implications for Federal Rescheduling Debate

The McGill study arrives as DEA weighs a proposed rule to move cannabis from Schedule I to Schedule III under the Controlled Substances Act, 21 U.S.C. § 812. Published as NPRM docket DEA-407 in May 2024, the rescheduling proposal triggered more than 43,000 public comments. Many cited harm-reduction potential as justification for loosening federal restrictions.

Critics of the current Schedule I classification argue the McGill findings undercut DEA's longstanding position that cannabis has no accepted medical use. When will the agency finalize the rescheduling rule? It hasn't said.