Health & Biomedical Sciences Faculty Publications
Document Type
Article
Publication Date
4-13-2026
Abstract
The Affordable Care Act (ACA) allowed states to expand Medicaid eligibility, potentially improving access to care and reducing psychological distress among lower-income adults. However, evidence on population-level mental health effects remains mixed, and conventional two-way fixed-effects difference-in-differences (DiD) estimates can be biased under staggered adoption. This study estimates the effect of Medicaid expansion on frequent mental distress (FMD) among non-elderly adults, with emphasis on lower-income adults. We used Behavioral Risk Factor Surveillance System (BRFSS) data from 2011 to 2024 and restricted the sample to adults aged 18 to 64 years. FMD was defined as ≥14 days of poor mental health in the past 30 days. Medicaid expansion was assigned by state implementation year. For transparent weighting and computational feasibility, we collapsed microdata to state-year prevalence using BRFSS survey weights and applied prespecified minimum cell-size and effective-sample screens (lower-income panel: unweighted N ≥ 150 and Kish n_eff ≥ 50; pooled and higher-income panels: n_eff ≥ 200). We estimated group-time average treatment effects using the Callaway-Sant'Anna staggered DiD framework (csdid), clustered standard errors at the state level, and used pair-balanced observations when panels were unbalanced. Income strata were defined using BRFSS household income categories (lower-income: inc_cat = 1; higher-income: inc_cat ∈ {7,8}) and are interpreted as economic-status proxies rather than Medicaid eligibility. In the lower-income state-year panel (353 state-years), Medicaid expansion was not associated with a statistically significant change in FMD (ATT -0.0125; 95% CI -0.0521 to 0.0271; P = .54). Estimates in the higher-income (656 state-years) and pooled (709 state-years) panels were similarly small and not statistically significant. Event-time estimates indicated modest heterogeneity at selected leads/lags without a consistent post-expansion pattern. Medicaid expansion was not associated with significant reductions in population-level frequent mental distress during 2011 to 2024. Any mental health effects appear modest and heterogeneous across cohorts and follow-up periods, suggesting that insurance expansion alone may be insufficient to shift population psychological distress without complementary behavioral health capacity and upstream social supports.
Recommended Citation
Adegoke, A., Adegoke, K., Durojaye, O. A., Dawodu, D., Aluko, A. I., Adekoya, A., & Knapp, K. A. (2026). Medicaid Expansion and Frequent Mental Distress Among U.S. Adults: Staggered DiD Using BRFSS, 2011 to 2024. Inquiry : a journal of medical care organization, provision and financing, 63, 469580261441768. https://doi.org/10.1177/00469580261441768
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Publication Title
Inquiry
DOI
10.1177/00469580261441768
Comments
© The Author(s) 2026
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