poverty, stress, memory

An article in the Economist reports on a study that seems to show that poverty causes stress in children and this erodes their working memory:

"THAT the children of the poor underachieve in later life, and thus remain poor themselves, is one of the enduring problems of society. Sociologists have studied and described it. Socialists have tried to abolish it by dictatorship and central planning. Liberals have preferred democracy and opportunity. But nobody has truly understood what causes it. Until, perhaps, now.
...
To measure the amount of stress an individual had suffered over the course of his life, the two researchers used an index known as allostatic load. This is a combination of the values of six variables: diastolic and systolic blood pressure; the concentrations of three stress-related hormones; and the body-mass index, a measure of obesity. For all six, a higher value indicates a more stressful life; and for all six, the values were higher, on average, in poor children than in those who were middle class. Moreover, because Dr Evans’s wider study had followed the participants from birth, the two researchers were able to estimate what proportion of each child’s life had been spent in poverty. That more precise figure, too, was correlated with the allostatic load.

The capacity of a 17-year-old’s working memory was also correlated with allostatic load. Those who had spent their whole lives in poverty could hold an average of 8.5 items in their memory at any time. Those brought up in a middle-class family could manage 9.4, and those whose economic and social experiences had been mixed were in the middle.

These two correlations do not by themselves prove that chronic stress damages the memory, but Dr Evans and Dr Schamberg then applied a statistical technique called hierarchical regression to the results. They were able to use this to remove the effect of allostatic load on the relationship between poverty and memory discovered originally by Dr Farah. When they did so, that relationship disappeared. In other words, the diminution of memory in the poorer members of their study was entirely explained by stress, rather than by any more general aspect of poverty.

To confirm this result, the researchers also looked at characteristics such as each participant’s birthweight, his mother’s age when she gave birth, the mother’s level of education and her marital status, all of which differ, on average, between the poor and the middle classes. None of these characteristics had any effect. Nor did a mother’s own stress levels.

That stress, and stress alone, is responsible for damaging the working memories of poor children thus looks like a strong hypothesis."

awful thought, right? maybe I'm not understanding how the statistical techniques work, but I might also want to look at whether the quality of the schools the kids went to had any impact.

Just for context: "Children are considered to be living in poverty if their family income, before taxes, falls below the poverty thresholds set by the federal government for families of different sizes....In 2005, the poverty threshold for a single parent and two children was $15,735; for a married couple with two children the poverty threshold was $19,806 ... In 2005 (the latest year available), the highest rates of child poverty occurred in three of the five boroughs of NYC: Bronx (39.4%), Kings (which includes Brooklyn) (30.9%) and New York (29.9%)."

If you don't live in NYC, please understand that the conditions kids live in here are even more dire than in other parts of the country, simply because $15,735 doesn't go nearly as far here.

(info from the NY State Kids Well-Being Clearinghouse)