Document Type : Original Article
Department of Family Medicine, Charles Drew University, Los Angeles, CA, USA
Department of Urban Public Health, Charles Drew University, Los Angeles, CA, USA
College of Literature, Sciences, and the Arts, University of Michigan, Ann Arbor, MI, USA
Introduction: While socioeconomic status (SES) indicators such as household income are known to be associated with larger cortical surface area, recent research on Marginalization-related Diminished Returns (MDRs) suggests that family SES indicators such as household income may have weaker effects on brain function and structure for non-White (marginalized) than White (privileged) families: a pattern that reflects structural and societal inequalities deeply intertwined into the United States social fabric.
Methods: This is a cross-sectional study that used baseline data from the Adolescent Brain Cognitive Development (ABCD) study. Data was collected between 2016 and 2018. Overall, 6039 9–10-year-old children entered our analysis. The independent variable was household income. The moderator was race. The primary outcome was the overall cortical surface area. Age, sex, and family structure were the covariates. We used mixed effects regression models that adjusted for data analysis because ABCD data is nested into families, centers, and US states.
Results: While high household income was associated with larger cortical surface area, this effect was weaker for Asian than non-Hispanic White children. This racial heterogeneity in the effects of household income on cortical surface area was documented by a statistically significant interaction between race and household income on cortical surface area.
Conclusion: For American children, household income does not similarly correlate with cortical surface area of diverse racial groups. Brain development in the US is not solely a function of SES (availability of resources) but also how social groups are racialized and treated in the society. In the US, race, as a proxy of racism, limits how much SES can affect brain structures such as cerebral cortex. Due to racialization, segregation, discrimination, and marginalization, racial minority children may experience weaker effects of SES. Structural inequalities should be addressed to equalize the return of SES resources across racially diverse families.