Scholars and social observers have long known that poverty has many adverse consequences — a conclusion that would probably come as no surprise to people subsisting at society’s lowest economic margins. But a new study, coauthored by Amitabh Chandra, of Harvard Kennedy School, indicates that growing up poor may pose another, less visible risk that was not recognized before: neuroanatomical changes in the brain itself.
“Prior research has linked poverty with a myriad of deleterious outcomes, from poor health to lower educational achievement,” the study authors write. “Yet there is little currently understood about the neurobiological mechanisms leading to these socioeconomic disparities.”
The researchers theorized that there might be distinct structural differences in the brain that correlate with income. Such differences, they proposed, would be pronounced in the hippocampus — a brain region associated with learning, memory, and other key functions. To test their hypothesis, Chandra and his coauthors at the University of Wisconsin reviewed brain-scan data from a National Institutes of Health study of brain development. From this sample, the team chose to analyze more than 300 subjects — children and adolescents four to eighteen years old — across a range of household income levels, from below $5,000 a year to above $100,000.
As theorized, the researchers uncovered a relation- ship between income and the hippocampus. In particular, they found that the density of gray matter (or brain cells) in the hippocampus tended to increase with income. Children from financially deprived backgrounds had lower concentrations of gray matter in this brain region than their more affluent counterparts. Interestingly, no link was detected between income and gray matter in the amygdala, another brain area, indicating that the observed effect was specific to the hippocampus but did not apply to the brain as a whole.
“Taken together, these findings suggest that differences in the hippocampus, perhaps due to stress tied to growing up in poverty, might partially explain differences in long-term memory, learning, control of neuroendocrine functions, and modulation of emotional behavior,” the authors write. Yet Chandra emphasizes that one should not conclude that cognitive performance is automatically affected by anatomical development: “Do these children do worse in school or on tests because of the differences in their hippocampi, or is the brain able to compensate? Future studies need to look not only at brain structure but at brain function as well.”
But if anatomical development and cognitive performance are causally linked, the authors’ work suggests that early interventions are more likely to be beneficial than later ones. Beyond that, uncertainties abound. “We can say that poverty appears to be associated with these neuroanatomical changes, but what is it about poverty?” Chandra adds. “Is it stress? Is it nutrition? Is it stimulation? Are the lives of poorer parents so chaotic that they can’t read to their children on a regular basis?” Each of these contributing factors would have a different policy step associated with it.
At the same time, Chandra is struck by the fact that the links between poverty and anatomical development are far from deterministic. “There are millions of kids who have experienced high levels of poverty who go on to do great things in their lives,” he notes. “So we don’t think that it’s a deterministic model — that you are born poor and therefore your brain is doomed.”
Chandra is not surprised by the fact that the study may raise more questions than it answers. “It’s only through precise measurements that you find out what you know and what you don’t know,” he says. “I can’t think of an area of public policy that is more important than policies related to children and their development. This also happens to be an area where better measurements would really help.”
— by Steve Nadis