The impact of Medicaid expansion on mental health and substance use related inpatient visits

Objective: Under the Affordable Care Act, many states expanded their Medicaid eligibility, allowing individuals living at or below 138% of the Federal Poverty Level to receive insurance coverage. As a result, forty states and the District of Columbia have expanded Medicaid to date. Although Medicaid expansion is expected to increase access to care in general, it is not evident if it has helped increase access to mental health and substance use-related healthcare, especially in inpatient settings. Therefore, this study examines the impact of Medicaid expansion on mental health and substance use- (MHSU) related inpatient visits and the variation in payer mix. Methods: This study utilizes state-level quarterly inpatient visit data from the Healthcare Cost and Utilization Project's Fast Stats Database from 2005 to 2019 and performs difference-in-differences regression analyses to compare MHSU-related inpatient visit data in expansion and non-expansion states for all visits and by payer. Analyses controlled for state-level socio-demographic and health policy variables. Results: Findings indicate that Medicaid expansion did not significantly affect overall MHSU-related inpatient visits. However, Medicaid expansion was associated with 22.74% increase (P < 0.01; 95% CI: 17.76, 27.71) in the Medicaid share of MHSU-related inpatient visits, 18.31% reduction (P < 0.01; 95% CI: −22.54, −14.09) in the uninsured share of MHSU-related inpatient visits, and 4.42% reduction (P < 0.05; 95% CI: −7.83, −1.01) in the privately insured share of MHSU-related inpatient visits in expansion states compared with non-expansion states. Conclusions: Findings show that Medicaid expansion significantly affects the payer mix associated with MHSU-related inpatient visits while it has no significant impact on the overall MHSU-related inpatient visits.