Medical Cannabis Laws Linked to Less Frequent Opioid Misuse | Research

The takeaway

States with medical cannabis laws saw shifts from frequent to occasional non-medical opioid use, with the strongest effect among people with cannabis use disorder.

Policy researchers, public health officials, and anyone interested in how cannabis laws interact with the opioid crisis.

What the researchers found

Medical cannabis laws were associated with a 1.5 percentage point decrease in frequent non-medical prescription opioid use and a 2.1 percentage point increase in occasional use, suggesting a shift in use patterns rather than overall reduction.

Why it matters

The opioid crisis has prompted interest in whether cannabis access might reduce opioid harms. This study suggests the relationship is more nuanced than simple substitution, with shifts in frequency patterns concentrated among people who also have cannabis use disorder.

The numbers in context

MCL associated with +2.1 percentage points occasional use (95% CI: 0.5, 3.8), -0.6 percentage points regular use (95% CI: -1.1, -0.1), -1.5 percentage points frequent use (95% CI: -2.7, -0.4). Among those with cannabis use disorder: +5.6 pp occasional (95% CI: 1.5, 9.6), -4.9 pp frequent (95% CI: -8.1, -1.8).

How the study worked

Multi-level mixed effects models analyzed nationally representative survey data from U.S. adults reporting past-year non-medical prescription opioid use across the 2004-2014 National Surveys on Drug Use and Health, comparing states with and without medical cannabis laws.

What this study cannot tell us

Observational design cannot establish causation. Self-reported data from 2004-2014 may not reflect current cannabis markets. MCL implementation varied widely across states. The study could not assess specific products or doses used.

How to read the evidence

Large nationally representative sample with appropriate statistical methods, but observational design limits causal inference.

When this study was published

Published 2025, using 2004-2014 NSDUH data.

The bigger picture

This adds to a mixed evidence base on cannabis-opioid substitution. The finding that frequency shifts were driven by people with cannabis use disorder complicates the narrative that cannabis access broadly reduces opioid misuse. It raises questions about tradeoffs between reducing opioid harm and increasing cannabis-related risk.

Questions still open

Whether these frequency shifts translate into meaningful reductions in opioid-related harms like overdose
How recreational cannabis legalization (vs. medical only) affects these patterns

Common questions

Did medical cannabis laws reduce overall opioid misuse?

Not exactly. The total number of people misusing opioids did not clearly decline. Instead, the pattern shifted: more people used occasionally rather than frequently.

Why were the effects strongest among people with cannabis use disorder?

The researchers suggest these individuals may be most likely to substitute cannabis for opioids, but this group also faces its own risks from heavy cannabis use.

Read the original research

Association Between Legal Access to Medical Cannabis and Frequency of Non-Medical Prescription Opioid Use Among U.S. Adults.

International journal of mental health and addiction, 23(2), 1663-1676

View on PubMed ↗Publisher’s paper ↗

Citation

Samples, Hillary; Levy, Natalie S; Bruzelius, Emilie; Segura, Luis E; Mauro, Pia M; Boustead, Anne E; Mauro, Christine M; Martins, Silvia S. (2025). Association Between Legal Access to Medical Cannabis and Frequency of Non-Medical Prescription Opioid Use Among U.S. Adults.. International journal of mental health and addiction, 23(2), 1663-1676. https://doi.org/10.1007/s11469-023-01191-y