Top baboons in a stable dominance hierarchy have lower stress-hormone levels than do subordinates. But throwing a new monkey in the mix sends stress hormones soaring as troop members jockey for dominance. When Sapolsky is not in Africa watching baboons behaving badly, he studies stressed-out rats in his lab at Stanford, where he is a professor in the Department of Biological Sciences and in the Department of Neurology and Neurological Sciences. Stress exerts its strongest effects on gastrointestinal function, sleep, sex drive and blood pressure. In fact, he says, Type A behavior is a greater risk factor for cardiovascular disease than smoking.
Stress has lesser effects on diabetes, immune function and brain aging.
But you must absolutely flatten the immune system to hurt tumor defense, and the effects of stress on the immune system are never that severe. The good news is that your mind is a powerful tool for de-stressing your body. The bad news is that the brain cells that turn off the body's stress response are the first neurons to succumb to stress. Its predominant functions are learning and memory. Stress-hormone levels tend to rise with age, and hippocampal cells express fewer hormone receptors on their surfaces to protect themselves from the excess.