Background and objectives: Mental and physical health are influenced by a complex interplay of environmental, socioeconomic, and demographic factors, yet county-level determinants and their differential effects on these outcomes remain underexplored. Accordingly, this study examines the associations between a comprehensive set of environmental, socioeconomic, and demographic factors and county-level mental and physical health outcomes in the U.S., with particular attention to differences in their determinants.

Materials and Methods: Data from 2145 counties were analyzed, focusing on the percentage of adults experiencing frequent mental distress and frequent physical distress, defined as 14 or more days of poor health per month. Descriptive analyses summarized outcome distributions and their associations with county characteristics, while multivariate ordinary least squares regressions with state-clustered standard errors identified significant predictors across living environment, socioeconomic, and demographic domains.

Results: Housing quality, insufficient sleep, and access to healthy food were significantly associated with both mental and physical distress, with mental health particularly sensitive to housing and sleep challenges. Educational attainment and household income were negatively associated with both outcomes, while poverty was positively associated with distress across domains. Demographic factors showed outcome-specific patterns: female population share was associated with both mental and physical health, non-Hispanic white population share was significant only for mental health, rurality only for physical health, and older age was negatively associated for physical but not mental distress.

Conclusion: These findings highlight that county-level structural, socioeconomic, and demographic characteristics were jointly associated with mental and physical health, with both shared and outcome-specific effects, offering guidance for targeted public health interventions, resource allocation, and policy development.

January 2026; Vol. 20(1):009.  DOI: https://doi.org/10.55010/imcjms.20.009

*Correspondence:Fang Fang, California State University, Los Angeles, 5151 State University Drive, Los Angeles, U.S.,90032. Email: ffang2@calstatela.edu.

© 2026 The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License(CC BY 4.0)