Medicaid coverage in substance use disorder treatment after the affordable care act.

The Affordable Care Act (ACA) prompted sweeping changes to Medicaid, including expanding insurance coverage to an estimated 12 million previously uninsured Americans, and imposing new parity requirements on benefits for behavioral health services, including substance use disorder treatment. Yet, limited evidence suggests that these changes have reduced the number of uninsured in substance use disorder treatment, or increased access to substance use disorder treatment overall. This study links data from a nationally-representative study of outpatient substance use disorder treatment programs and a unique national survey of state Medicaid programs to capture changes in insurance coverage among substance use disorder treatment patients after ACA implementation. Medicaid expansion was associated with a 15.7-point increase in the percentage of patients insured by Medicaid in substance use disorder treatment programs and a 13.7-point decrease in the percentage uninsured. Restrictions in state Medicaid benefits and utilization policies were associated with a decreased percentage of Medicaid patients in treatment. Moreover, Medicaid expansion was not associated with a change in the total number of clients served over the study period. Our findings highlight the important role Medicaid has played in increasing insurance coverage for substance use disorder treatment.