Medicaid expansion for undocumented adults and its association with health insurance coverage among noncitizens in California, 2017-2023.

Introduction: California's 4.8 million noncitizen adults, half of whom are undocumented, endure substantial exclusions from health care. To address this gap, California policymakers expanded full-scope, state-funded Medicaid without discriminating by immigration status, first extending coverage to undocumented young adults (18-25 years) in 2020 and then to older adults (≥50 years) in 2022. Methods: Using the American Community Survey (2017-2023), we assessed whether California's Medicaid expansion for young and older undocumented adults was associated with changes in insurance coverage by comparing pre- and post-expansion differences between citizens and noncitizens (difference-in-differences). Results: Compared to citizens, the expansion was not associated with increased health insurance or Medicaid enrollment among young noncitizens. However, among older adults, the expansion was associated with a modest 1.3% increase in overall insurance coverage for noncitizens, including a 2.4% increase in Medicaid. Following these expansions, noncitizens remain significantly less likely to have insurance: 28% of young noncitizens and 16% of older noncitizens lack coverage, compared to 8% and 3% for young and older citizens, respectively. Conclusion: Given these persistent inequities-where noncitizens across nearly all sociodemographic factors are less likely to be insured-preserving and strengthening the existing pathways to insurance coverage for noncitizens, including undocumented immigrants, remains critical.