Cannabis Legalization and Opioid Prescribing in Veterans Health Administration Patients: 2013-2022.

Mannes Z.; Wall M.; Stohl M.; Malte C.; Olfson M.; Livne O.; Fink D.; Simpson T.; Wisell C.; Keyhani S. et al. · Journal of general internal medicine · 2026

**Background & Methods** This retrospective cohort study examined Veterans Health Administration electronic health records from 2013-2022 to assess associations between state cannabis legalization (medical [MCL] and/or recreational [RCL]) and opioid prescribing patterns among 18-75 year-old patients with chronic pain diagnoses. A staggered-adoption difference-in-differences analysis was employed to estimate causal effects, comparing opioid prescribing trends before and after cannabis law enactment across states with varying legal statuses. **Key Findings** • Medical cannabis legalization was associated with modest reductions in opioid prescribing: ≥30-day opioid use decreased by 0.79 percentage points (95% CI, -0.86 to -0.71) and long-term opioid therapy decreased by 0.34 percentage points (95% CI, -0.40 to -0.28), but high-dose opioid prescribing and opioid/benzodiazepine co-prescriptions showed minimal or counterintuitive changes. • Recreational cannabis legalization (compared to MCL-only states) yielded additional reductions in ≥30-day opioid prescribing (-0.14 percentage points), high-dose opioid prescribing (-0.33 percentage points), and opioid/benzodiazepine co-prescribing (-0.33 percentage points). • Age-stratified analyses revealed that associations were generally more pronounced and consistent in adults aged 65-75 years compared to younger age groups, suggesting differential treatment responses across age demographics. **Dosage & Administration** Not reported. The study examined prescription patterns rather than specific dosing regimens or administration routes. **Safety & Adverse Effects** Not reported. This study focused on opioid prescribing patterns associated with cannabis legalization and did not assess adverse effects of cannabis use or safety outcomes. **Evidence Quality** Strengths include use of real-world VHA data spanning nearly a decade with a large patient population and rigorous difference-in-differences methodology. Limitations include restriction to VHA patients (primarily older, male veterans), inability to assess actual cannabis use or patient substitution behaviors, and potential unmeasured confounding from concurrent policy changes or prescribing guideline updates. The modest effect sizes and inconsistent findings across outcome measures (particularly high-dose opioids) suggest clinical significance remains uncertain. This observational study provides low-to-moderate quality evidence suitable for informing healthcare policy discussions but cannot establish definitive causal mechanisms.

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