State sanctuary policies and the immigration enforcement activities across US counties: implications for population health.

Introduction: Recent increases in US immigration enforcement may contribute to an anti-immigrant environment that poses serious health and social risks. In response, several states have enacted sanctuary policies limiting cooperation with federal immigration authorities, though their population-level impacts remain unclear. This study estimated associations between state sanctuary policy enactment and county-level public program participation by baseline immigration enforcement. Methods: County-level data from 2011 to 2023 were obtained from the American Community Survey and Syracuse Transactional Records Access Clearinghouse. Outcomes included county-level Medicaid and Supplemental Nutrition Assistance Program (SNAP) participation. Sanctuary policies were modeled as a time-varying exposure using a staggered difference-in-differences framework, with analyses stratified by baseline immigration enforcement. Results: We found no statistically significant association between sanctuary policy enactment and Medicaid or SNAP enrollment per 10 000 likely eligible individuals in counties with high baseline enforcement; however, estimated percent changes were positive (Medicaid percent change: 28.6, 95% CI: -14.9, 94.3; SNAP: 9.9, 95% CI: -81.6, 557.5). In counties with low baseline enforcement, associations were not statistically significant, and estimates were smaller in magnitude. Conclusion: These findings suggest that protective immigration policies may partially mitigate chilling effects and promote engagement with social supports among eligible populations. However, estimates should be interpreted cautiously given the limited number of treated states.