Research Links Poor Children's Stress and Brain Impairment
Monday, April 6, 2009
Children raised in poverty suffer many ill effects: They often have health problems and tend to struggle in school, which can create a cycle of poverty across generations.
Now, research is providing what could be crucial clues to explain how childhood poverty translates into dimmer chances of success: Chronic stress from growing up poor appears to have a direct impact on the brain, leaving children with impairment in at least one key area -- working memory.
"There's been lots of evidence that low-income families are under tremendous amounts of stress, and we know that stress has many implications," said Gary W. Evans, a professor of human ecology at Cornell University in Ithaca, N.Y., who led the research. "What this data raises is the possibility that it's also related to cognitive development."
With the economic crisis threatening to plunge more children into poverty, other researchers said the work offers insight into how poverty affects long-term achievement and underscores the potential ramifications of chronic stress early in life.
"This is a significant advance," said Bruce S. McEwen, who heads the laboratory of neuroendocrinology at Rockefeller University in New York. "It's part of a growing pattern of understanding how early life experiences can have an influence on the brain and the body."
Previous research into the possible causes of the achievement gap between poor and well-off children has focused on genetic factors that influence intelligence, on environmental exposure to toxins such as lead, and on the idea that disadvantaged children tend to grow up with less intellectual stimulation.
"People have hypothesized both genetic and environmental factors play a role in why poor children don't do as well in school," said Martha Farah, director of the center for cognitive neuroscience at the University of Pennsylvania. "Experiential factors can include things like having fewer trips to museums, having fewer toys, having parents who don't have as much time or energy to engage with them intellectually -- to read to them or talk to them."
But Evans, who has been gathering detailed data about 195 children from households above and below the poverty line for 14 years, decided to examine whether chronic stress might also be playing a role.
"We know low-socioeconomic-status families are under a lot of stress -- all kinds of stress. When you are poor, when it rains it pours. You may have housing problems. You may have more conflict in the family. There's a lot more pressure in paying the bills. You'll probably end up moving more often. There's a lot more demands on low-income families. We know that produces stress in families, including on the children," Evans said.
For the new study, Evans and a colleague rated the level of stress each child experienced using a scale known as "allostatic load." The score was based on the results of tests the children were given when they were ages 9 and 13 to measure their levels of the stress hormones cortisol, epinephrine and norepinephrine, as well as their blood pressure and body mass index.
"These are all physiological indicators of stress," said Evans, whose findings were published online last week by the Proceedings of the National Academy of Sciences. "The basic idea is this allows you to look at dysregulation resulting from stress across multiple physiological systems."
The subjects also underwent tests at age 17 to measure their working memory, which is the ability to remember information in the short term. Working memory is crucial for everyday activities as well as for forming long-term memories.