Rule #8: Stressed brains don't learn the same way

Your body's defense system--the release of adrenaline and cortisol--is built for an immediate response to a serious but passing danger, such as a saber-toothed tiger. Chronic stress, such as hostility at home, dangerously deregulates a system built only to deal with short-term responses.
Under chronic stress, adrenaline creates scars in your blood vessels that can cause a heart attack or stroke, and cortisol damages the cells of the hippocammpus, crippling your ability to learn and remember.
Individually, the worst kind of stress is the feeling that you have no control over the problem--your are helpless.
Emotioanl stress has huge impacts across society, on children's ability to learn in school and on employees' productivity at work.