The California 2020 Medi-Cal Expansion to Young Adults and Coverage Among Noncitizens.

Importance: Undocumented immigrants are more than 5 times as likely as US citizens to be uninsured. Before 2020, undocumented young adults aged 19 to 25 years in California were eligible for restricted-scope Medi-Cal, which only covers emergency services. Objective: To examine the association of the California 2020 full-scope Medi-Cal expansion to young adults aged 19 to 25 years regardless of immigration status with coverage outcomes and to assess subgroup differences by race and ethnicity, sex, and age. Design, Setting, and Participants: This cross sectional study included American Community Survey respondents who were noncitizens aged 19 to 25 years before (2016-2019) and after (2021-2022) the policy's implementation in California; the treatment group was compared with California noncitizens aged 26 to 32 years and young adults aged 19 to 25 and 26 to 32 years from 6 comparison states (Arizona, Florida, Illinois, Nevada, New York, and Texas). Analysis was conducted from January 2024 to August 2025. Exposure: California's 2020 Medi-Cal expansion. Main Outcomes and Measures: Triple difference analysis was used to estimate the association of the California Medi-Cal expansion with health insurance coverage (any, Medicaid, and private coverage) among noncitizens aged 19 to 25 years relative to California noncitizens aged 26 to 32 years and young adults in the 6 comparison states. Results: The sample included 19 773 and 32 515 noncitizen American Community Survey respondents in California aged 19 to 25 years and 26 to 32 years, respectively, and 28 535 and 43 213 individuals aged 19 to 25 years and 26 to 32 years, respectively, residing in comparison states. Baseline weighted percentages for the 19- to 25-year treatment group included 52.1% (95% CI, 51.0%-53.2%) male, 31.9% (95% CI, 30.7%-33.0%) Asian non-Hispanic, 1.8% (95% CI, 1.5%-2.2%) Black non-Hispanic, 54.6% (95% CI, 53.4%-55.9%) Hispanic, 9.7% (95% CI, 8.9%-10.5%) White non-Hispanic, and 2.0% (95% CI, 1.6%-2.3%) other race non-Hispanic. Medi-Cal expansion was associated with a 4.2 (95% CI, 1.3-7.1)-percentage-point increase in Medicaid and a 3.5 (95% CI, 0.2-6.8)-percentage-point increase in any coverage. In subgroup analyses, percentage-point increases in Medicaid were statistically significant for Hispanic young adults (6.7 [95% CI, 2.6-10.9] percentage points), males (3.6 [95% CI, 0.1-7.1] percentage points), females (5.0 [95% CI, 0.7-9.3] percentage points), those aged 19 to 22 years (4.4 [95% CI, 0.7-8.1] percentage points), and those aged 23 to 25 years (4.0 [95% CI, 0.7-7.3] percentage points). In post hoc analyses, the estimates translated to increases in Medi-Cal and any coverage of 24.4 and 20.3 percentage points, or 30 665 and 25 554 young adults, respectively. Conclusions and Relevance: In this cross-sectional study, the California 2020 Medi-Cal expansion was associated with significant coverage gains. Because the American Community Survey did not distinguish between restricted- and full-scope Medi-Cal, the analysis may have underestimated coverage increases, and further research is warranted to understand the health care and economic costs and benefits of California's expansion.