Study: Poor kids' stress affects brain

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 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.

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.

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.

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. When the researchers analyzed the relationships among how long the children lived in poverty, their allostatic load and their later working memory, they found a clear relationship: The longer they lived in poverty, the higher their allostatic load and the lower they tended to score on working-memory tests. Those who spent their entire childhood in poverty scored about 20 percent lower on working memory than those who were never poor, Evans said.

Relief from itch found in nerves

NEW YORK — Scratch an itch and you get ... aaaaaah. Now scientists have watched spinal nerves transmit that signal to the brain in monkeys, a possible step toward finding new treatments for persistent itching in people.

More than 50 conditions can cause serious itching, including AIDS, Hodgkin's disease and the side effects of chronic pain treatment, said Glenn Giesler, Jr., a neuroscientist at the University of Minnesota in Minneapolis.

Scratching can lead to serious skin damage and infections, he said. So scientists want to find ways for such people to relieve their distress "without tearing up their skin," he said.

In a federally funded study, reported Monday on the Web site of the journal Nature Neuroscience by Giesler and colleagues, researchers sedated long-tailed macaques and placed recording electrodes on their spinal nerves. They injected a chemical into the skin to produce itching. The nerves fired electrical signals.

Then the researchers scratched the leg with a hand-held metal device that simulates three monkey fingers. The firing rate dropped.

In contrast, when researchers scratched the leg without causing an itch first, the firing rate jumped. So the nerves somehow "know" to react much differently if there's an itch to be relieved than if there isn't.

"It's like there's a little brain" in the spinal cord, Giesler said.