Neighborhood Poverty and Brain Development: Adaptation or Maturation, Fixed or Reversible?

In this cross-sectional study, Taylor et al1 ask whether neighborhood poverty, over and above household income, accounts for variance in brain and cognitive development in a large sample of 11 875 children aged 9 to 10 years. This cross-sectional data set is taken from the ongoing longitudinal Adolescent, Brain, and Cognitive Development (ABCD) study, which follows thousands of children from childhood through adolescence. Taylor and colleagues1 report that neighborhood poverty accounts for differences in prefrontal and hippocampal volumes as well as several cognitive tasks. This work advances the field in several ways. First, the power of the collaborative ABCD project is on display, with ample sample size and rich measures. Second, the mechanistic insight offered by the structural equation modeling, namely the analysis associating neighborhood poverty, reading, and oral vocabulary scores with hippocampal and prefrontal cortical volumes, lays the foundation for future work. This finding raises the possibility, open to empirical scrutiny, that school quality may directly shape brain and cognitive development. Finally, and perhaps most importantly, there is value in shifting the scientific focus from the shaping power of household income to that of neighborhood poverty. This is a key contribution to understanding the embedded ecological contexts that children grow and thrive in. Indeed, the findings by Taylor and colleagues1 may be reciprocally informative to convergent data from economists at the Opportunity Insights Project based at Harvard University. The broad goal of this project is to use large-scale data to determine how best to alleviate barriers to economic opportunity in the US. In a relevant 2018 study from this group, Chetty and Hendren2 examined tax data from 1996 to 2012 from millions of families who moved across counties in the United States, asking specifically whether income in adulthood is associated with the counties where children grew up. They define a high opportunity area as an area that supports intergenerational mobility (ie, an offspring’s adult income that is higher than their parents’ income was). Chetty and Hendren2 estimated that each year living in a county with 1-SD higher opportunity than the county a person at the 25th percentile of the income distribution was born into was associated with a 10% higher adult income. In a different 2016 study, Chettey and Hendren3 found that moving to a higher opportunity county in childhood was associated with higher adult income in proportion to the amount of time the child spent in the county. The results of the study by Taylor et al1 results complement those of these studies by Chetty and Hendren2,3 with supportive data from cognitive and brain development in children. The 2016 findings from Chetty and Hendren,3 that is, that moving to a higher opportunity area in childhood is associated with changes in adult income outcomes, raises the empirically testable possibility that the outcomes reported by Taylor et al1 are reversible and, in being so, may not reflect brain and cognitive maturation but rather environmental adaptation. One theoretical frame on child development is that it is a dynamic movement of a plastic resilient organism as it ontogenetically adapts to changes in the body and challenges in the environment.4,5 In keeping with this framework, there are 2 possible interpretations of the findings reported by Taylor et al.1 One is that neighborhood poverty is associated with unfavorable brain and cognitive outcomes when compared with neighborhood affluence. The alternative is that children in each neighborhood are developing in a way that supports their own survival needs, that is, they have similarly good or favorable developmental courses for survival in their own environments. + Related article