"Volunteers gave saliva samples so that researchers could analyze it for the stress hormone cortisol. Researchers found that cortisol reactivity was related to parental responsivity, and the less parental responsivity, the less of a normal stress response the volunteers had.
"You might say, 'Well, of course life is more stressful in lower socioeconomic strata,' " she said. "But the degree of magnitude of the stress that they live with is just unbelievable."
Such research points to the idea that stress leads to a stunting of brain development in children of low socioeconomic backgrounds. It is unknown whether that stunting can be reversed, but you shouldn't assume that it's unchangeable, Farah said."
Life How poverty might change the brain: