Importance: Medicaid is the largest payer of substance use disorder treatment in the US and plays a key role in responding to the opioid epidemic. However, as recently as 2017, many state Medicaid programs still did not cover the full continuum of clinically recommended care.

Objective: To determine whether state Medicaid fee-for-service (FFS) programs have expanded coverage and loosened restrictions on access to substance use disorder treatment in recent years.

Design, Setting, and Participants: In 2014, 2017, and 2021, a survey on coverage for substance use disorder treatment was conducted among state Medicaid programs and the District of Columbia with FFS programs. This survey was completed by Medicaid program directors or knowledgeable staff. Data analysis was performed in 2022.

Main Outcomes and Measures: The following were calculated for a variety of substance use disorder treatment services (individual and group outpatient, intensive outpatient, short-term and long-term residential, recovery support, inpatient treatment and detoxification, and outpatient detoxification) and medications (methadone, oral and injectable naltrexone, and buprenorphine): (1) the percentage of Medicaid FFS programs covering these services and medications and (2) the percentage of Medicaid FFS programs using utilization management policies, such as copayments, prior authorizations, and annual maximums.

Results: This study had response rates of 92% in 2014 and 2017 (47 of 51 states) and 90% in 2021 (46 of 51 states). For the 2021 wave, data are reported for the 38 non–managed care organization plan-only states. Between 2017 and 2021, coverage of individual and group outpatient treatment increased to 100% of states, and use of annual maximums for medications decreased to 3% or less (n ≤ 1). However, important gaps in coverage persisted, particularly for more intensive services: 10% of Medicaid FFS programs (n = 4) did not cover intensive outpatient treatment, 13% (n = 5) did not cover short-term residential care, and 33% (n = 13) did not cover long-term residential care. Use of utilization controls, such as copays, prior authorizations, and annual maximums, decreased but continued to be widespread.

Conclusions and Relevance: In this survey study of state Medicaid FFS programs, increases in coverage and decreases in use of utilization management policies over time were observed for substance use disorder treatment and medications. However, these findings suggest that some states still lag behind and impose barriers to treatment. Future research should work to identify the long-term ramifications of these barriers for patients.