Volume 55 | Number 4 | August 2020

Abstract List

Elson Oshman Blunt MA, Johanna Catherine Maclean, Ioana Popovici PhD, Steven C. Marcus PhD


To provide new evidence on the effects of large‐scale public health insurance expansions, associated with the Affordable Care Act (ACA), on the availability of specialty mental health care treatment in the United States. We measure availability with the probability that a provider accepts Medicaid.

Data Source/Study Setting

The National Mental Health Services Survey (N‐MHSS) 2010‐2018.

Study Design

A quasi‐experimental differences‐in‐differences design using observational data.

Data Collection

The N‐MHSS provides administrative data on the universe of specialty mental health care providers in the United States. Response rates are above 90 percent in all years. Data cover 85 019 provider/year observations.

Principal Findings

ACA‐Medicaid expansion increases the probability that a provider accepts Medicaid by 1.69 percentage points, 95 percent confidence interval: [0.0017,0.0321], which corresponds to an increase from 87.27 percent pre‐expansion to 90.27 percent postexpansion in expansion states or a 1.94 percent increase. We observe spillovers to Medicare, although this finding is sensitive to specification.


This study provides evidence on the impact of ACA‐Medicaid expansion on accepted forms of payment for specialty mental health care treatment. Findings suggest that expansion increases availability of providers who deliver valuable care for enrollees with severe mental illness. These findings may help policy makers reflecting on the future directions of the US health care delivery system.