Specialty substance use disorder treatment admissions steadily increased in the four years after medicaid expansion

The Affordable Care Act’s Medicaid expansion provided insurance coverage to many low-income adults with substance use disorders, but it is unclear whether this led to more people receiving treatment. We used the Treatment Episode Data Set and a difference-in-differences approach to compare annual rates of specialty treatment admissions in expansion versus nonexpansion states in the period 2010– 17. We found that admissions to treatment steadily increased in the four years after Medicaid expansion, with 36 percent more people entering treatment by the fourth expansion year in expansion states compared to nonexpansion states. Changes were largest for people entering intensive outpatient programs and those seeking medication treatment for opioid use disorder. The share of admissions paid for by Medicaid increased 23 percentage points in expansion states compared to nonexpansion states, largely displacing treatment paid for by state and local governments. The gradual increase in specialty substance use disorder treatment admissions after Medicaid expansion may reflect improving capacity and access to care.