Implementing parity for mental health and substance use treatment in Medicaid.

Abstract

To estimate the association between the implementation of parity in coverage for mental health and substance use disorder (MHSUD) services within the Medicaid program and MHSUD service use. Wisconsin Medicaid enrollment and claims data from 2013 to 2015. In April 2014, Wisconsin Medicaid transitioned childless adult beneficiaries from coverage with limited MHSUD services to parity-consistent coverage. Preparity, they only had Medicaid coverage for MHSUD visits to psychiatrists and the emergency department, while parent beneficiaries had parity-consistent coverage. The study uses a difference-in-differences design to compare outcome changes for childless adult and parent beneficiaries. We identified 76,569 childless adult and parent beneficiaries aged 18-64 who were continuously enrolled for the 2-year study period. Introducing parity-consistent coverage within Medicaid was associated with increased utilization of Medicaid-reimbursed MHSUD services: outpatient, prescription medication, ED, and inpatient. Increased MHSUD outpatient visits were driven by increased visits to nonpsychiatrists. Parity's effects on MHSUD service use have been studied in the context of private insurance, but its impact among Medicaid beneficiaries has not. Our findings suggest that parity implementation in Medicaid could increase access to effective MHSUD services in a high-need population.