The impact that socioeconomic inequities can have on a child’s hippocampal volume may have implications for their success and experience pursuing educational endeavors.
Emerging evidence has shown that children from families with lower income exhibit smaller hippocampal volume compared to children from families with higher income. However, research supported by the National Institute on Drug Abuse (NIDA) at the National Institutes of Health and published in Nature Communications has shown that the disparity in brain structure between children from high- versus low-income households was reduced by more than one-third in states where greater cash assistance was provided to families through anti-poverty programs. Additionally, disparities in mental health symptoms were reduced by nearly half in states with greater cash assistance available.
The impact that socioeconomic inequities can have on a child’s hippocampal volume may have implications for their success and experience pursuing educational endeavors. Specifically, the hippocampus plays a key role in memory and emotional learning. However, the study results demonstrate that this gap in brain development may potentially be mitigated through the implementation of state anti-poverty programs, such as Earned Income Tax Credit, Temporary Assistance for Needy Families, and Medicaid.
The research reflects data pulled from the NIDA-led Adolescent Brain Cognitive Development Study (ABCD Study). Investigators from Harvard University and Washington University, St. Louis, analyzed ABCD study data, which included more than 10,000 youth across 17 states with varying anti-poverty policies and levels of support offered around cost-of-living assistance.
“Multiple studies have found associations between the brain changes shown in this research and meaningful impacts such as low test scores, lack of school readiness, and risk factors for mood disorders,” said NIDA director Nora Volkow, MD, in a press release. “Investigating the policy factors that are associated with brain development and mental health is an important part of better understanding health inequities that impact people throughout their lives, starting in critical periods of development.”
When embarking on the study, the research team first replicated findings from smaller studies and validated that lower family income is associated with smaller hippocampal volume and more symptoms of mental health conditions—such as anxiety, depression, aggression, impulsivity, and inattention—among participants aged 9 to 11 years. Further, the investigators expected that disparities between families with a high versus low income would be exacerbated in more expensive states with a higher cost of living.
Based on their results, the investigators observed that this hypothesis was correct based on the data, as differences in hippocampal volume between children from high- and low-income families was more significant in states with a higher cost of living. However, in higher cost-of-living states with monetary assistance programs available, this disparity was reduced by 34%. Similarly, in states with Medicaid expansion, the disparity was reduced by 43%. Overall, the most expensive cost-of-living states with anti-poverty programs had narrower gaps in disparities around income-associated differences in brain structure. Additionally, states with the lowest cost of living also had similarly low income-associated differences in brain structure.
Furthermore, in expensive states where greater cash benefit is provided, the income-associated disparity in certain mental health symptoms, such as anxiety and depression, was 48% lower than in states with less cash benefit offered. When controlling for numerous state-level social, economic, and political characteristics—including population density, education equity, incarceration rates, and gender equity—these patterns remained significant.
“The association between brain structure and a low-resource environment is not an inevitability,” study author David Weissman, PhD, a postdoctoral fellow in the Stress and Development Lab at Harvard University, said in the press release. “Children’s brains are undergoing substantial development and have enhanced plasticity or capacity for further change based on their environment. These data suggest that policies and programs that work to reduce social and health inequities can directly reach children in disadvantaged environments and help support their mental health.”
The investigators did note that a limitation of this study is that it is correlational, so there are many other factors that could contribute to disparities in brain development and mental health along different income levels. In future research, the investigators hope to further assess impacts of experimental cash-assistance interventions, as well as other real-world policy changes, to observe how they impact differences in children’s mental health and brain structure development.
Weissman DG, Hatzenbuehler ML, Cikara M, Barch DM, McLaughlin KA. State-level macro-economic factors moderate the association of low income with brain structure and mental health in U.S. children. Nature Communications. 2023. doi:10.1038/s41467-023-37778-1