Foster Care, Substance Use, and Social Determinants of Health in South Carolina: A Geographic Approach

Foster care is a critical intervention for vulnerable children, with approximately 400,000 children entering the system annually in the United States. Parental substance use, second only to neglect, is now a leading cause of foster care entry. While previous research has explored the relationship between socioeconomic factors and foster care, few studies have incorporated spatial approaches at the neighborhood level to understand how factors such as economic inequality, healthcare disparities, and substance use influence foster care entries. This study addresses that gap by integrating spatial analysis and machine learning techniques to examine the geographic and social dynamics underlying foster care placements in South Carolina. Grounded in the Social Determinants of Health (SDH) framework, the research provides compelling evidence that substance use, poverty, and other SDH indicators are significant predictors of foster care entry, with pronounced spatial variation across the state. The findings reveal significant geographic clustering of substance use, particularly in the Pee Dee and Upstate regions, highlighting the critical role of local socioeconomic conditions—such as unemployment and healthcare access— in shaping substance use rates. Key predictors of foster care entry identified in the study include substance use, poverty, population density, and proximity to healthcare facilities at the census tract level. Geographically Weighted Regression (GWR) and spatially autoregressive models (spatial lag and spatial error) outperformed Ordinary Least Squares (OLS) models by capturing the spatial variability in the relationship between substance use and foster care entry, but also uncovered complex interactions. Notably, the analysis revealed a counterintuitive finding: proximity to treatment facilities was associated with higher foster care entry rates, likely due to proximity to urban centers, increased interaction with mandatory reporters, and challenges in treatment compliance. These findings highlight the importance of regionally tailored, geographically informed interventions that address the underlying socioeconomic and behavioral drivers of foster care placement. By focusing on specific geographic areas with high rates of substance use and foster care entries, policymakers and child welfare agencies can develop more effective, preventative strategies to support at-risk families and reduce the need for foster care placements.