Children who grow up in disadvantaged areas show faster declines in key indicators of brain development during adolescence compared to children in areas with more opportunities, a new study published in the journal cerebral cortex.
The brain undergoes dramatic changes during adolescence. Two of the most carefully studied metrics are cortical thickness (the thickness of the outer layer of the brain) and cortical surface area (the total surface area covered by the outer layer). Both typically decrease during the teenage years as the brain refines itself and becomes more efficient.
Scientists know that children from different socio-economic backgrounds show differences on these brain measures, but most previous research has focused on family-level factors such as parental income. Less attention has been paid to the broader neighborhood environment in which children grow up, including both its positive and negative attributes.
A research team led by Chloe Carrick from King’s College London analyzed brain imaging data collected from 11,639 children (48% female) enrolled in the American Adolescent Brain and Cognitive Development (ABCD) study at three time points, at approximately ages 10, 12 and 14.
Neighborhood disadvantage was measured using the Neighborhood Deprivation Index, which takes into account poverty levels, employment, and housing quality. Meanwhile, neighborhood educational and health/environmental opportunities were assessed using the Childhood Opportunity Index. The researchers used a statistical model to track individual differences in how each child’s brain changed over time, while controlling for family income, biological sex, and the type of MRI brain scanner used.
The study found that children who lived in more deprived areas at age 9 to 10 had lower cortical thickness and surface area to begin with, and that these measures declined faster as they progressed through adolescence.
In contrast, children in areas with more educational, health, and environmental opportunities had higher starting levels on both brain measures and their brains changed more slowly over the same time period.
These associations persist even after accounting for family income level, suggesting that the neighborhood environment contributes something more than can be explained by family economic status alone. Importantly, when analyzing the children’s brain developmental trajectories, the researchers found no clear distinct subgroups of children. Instead, differences continued to spread throughout the population, with no clear boundaries between groups.
The authors suggest that “growing up in disadvantaged areas may increase exposure to stressful stimuli such as community violence and environmental pollutants,” which may accelerate brain maturation as a survival adaptive response. Conversely, living in resource-rich areas may cause brain development to occur more slowly and over a longer period of time, extending the period of neuroplasticity and giving the brain more time to build complex connections.
However, the researchers note some limitations. The observed effect size was small. This means that although the patterns are realistic and statistically robust given the large sample size, they can only explain a limited portion of the between-individual variation. Furthermore, when the researchers performed a sensitivity analysis to control for overall brain size, the association between neighborhood disadvantage and the “pace” of cortical thinning was no longer statistically significant, suggesting that some of these specific relationships may be driven by differences in overall brain size.
The study, “Individual differences in cortical development during adolescence are associated with neighborhood characteristics: Longitudinal findings from the ABCD study,” was authored by Chloe Carrick, Divyangana Rakesh, Lea Michel, Kathryn Bates, and Delia Fuhrmann.
