Why You Stress and How to Stop

Your Brain on Stress

Mentally we're also at risk when stress levels skyrocket, and the damage can be dramatic. Stress can cause "structural and functional remodeling in the brain," says Bruce McEwen, PhD, Alfred E. Mirsky professor in the laboratory of neuroendocrinology at Rockefeller University in New York City. Much of the devastation happens in the hippocampus, a region that's vital to learning and making new memories. In one study, people with high levels of cortisol had a hippocampus that was 14 percent smaller than those whose cortisol levels were normal, and their memory was also impaired.

And stress can make us...s l o w. In tests, rats and mice that were stressed for several weeks took longer to learn new tasks than those who weren't, because their hippocampal nerve cells had atrophied. At the same time, the amygdala, the section of the brain that controls physical reactions, had grown larger, making the animals more anxious and aggressive. In other words, keep your stress level high for long enough and you will lose some ability to think -- and to calm down.