The impact of state medical marijuana policy implementation on opioid prescribing patterns among older adults: a difference-in-difference analysis

Objectives To assess the impact of state medical marijuana policy implementation on opioid prescribing patterns among older adults. Methods This study utilized the 5% national sample of 2012–15 Medicare administrative claims data. Beneficiaries age ≥ 65 were categorized into one of the following: Medical marijuana law implementation states, existing medical marijuana law states, and non-medical marijuana law states. A difference-in-difference analysis evaluated the impact of policy implementation on the yearly average total dose of prescription opioids filled per beneficiary. Key findings Among 449 336 Medicare beneficiaries included, 49.3% received at least one opioid prescription during the entire study period, while the proportion of individuals receiving at least one opioid prescription was significantly lower among medical marijuana law implementation states (42.7%) compared to non-medical marijuana law states (51.7%), and existing medical marijuana law states (47.2%). On average, beneficiaries in non-medical marijuana law states experienced a pre-to-post period (each 12 months in length) increase in morphine milligram equivalents that was 99.8 morphine milligram equivalents (MME) greater than the increase experienced by beneficiaries within implementation states (P < .001). In addition, beneficiaries in existing medical marijuana law states experienced an average pre-to-post period increase in morphine milligram equivalents that was 32.7 MME greater than the increase among implementation state beneficiaries (P = .023). Conclusions Medicare beneficiaries who were prescribed opioids or healthcare providers prescribing opioids may be replacing opioids with medical marijuana in states where medical marijuana is legislated. These results have implications for stakeholders by providing real-world evidence surrounding the viability of medical marijuana policy to decrease negative outcomes related to the opioid crisis.