Why Zebras Don't Get Ulcers: The Acclaimed Guide to Stress, Stress-Related Diseases, and Coping

by Robert M. Sapolsky

Yet the flu, in 1918 alone, killed many times more people than throughout the course of that most barbaric of conflicts, World War I.

Put in the parlance with which we have grown familiar, stress can make us sick, and a critical shift in medicine has been the recognition that many of the damaging diseases of slow accumulation can be either caused or made far worse by stress.

Essentially, we humans live well enough and long enough, and are smart enough, to generate all sorts of stressful events purely in our heads.

Viewed from the perspective of the evolution of the animal kingdom, sustained psychological stress is a recent invention, mostly limited to humans and other social primates.

And if someone spends months on end twisting his innards in anxiety, anger, and tension over some emotional problem, this might very well lead to illness.

The brain, it has been noted, has evolved to seek homeostasis.

A stressor is anything in the outside world that knocks you out of homeostatic balance, and the stress-response is what your body does to reestablish homeostasis.

Thus, the stress-response can be mobilized not only in response to physical or psychological insults, but also in expectation of them.

Homeostasis is about tinkering with this valve or that gizmo. Allostasis is about the brain coordinating body-wide changes, often including changes in behavior.

One of the hallmarks of the stress-response is the rapid mobilization of energy from storage sites and the inhibition of further storage.

During an emergency, it makes sense that your body halts long-term, expensive building projects.

Thus, during stress, digestion is inhibited—there isn’t enough time to derive the energetic benefits of the slow process of digestion, so why waste energy on it?

During stress, growth and tissue repair is curtailed, sexual drive decreases in both sexes; females are less likely to ovulate or to carry pregnancies to term, while males begin to have trouble with erections and secrete less testosterone.

With sufficiently sustained stress, our perception of pain can become blunted.

It is very rare, however, as we will see, that any of the crucial hormones are actually depleted during even the most sustained of stressors.

the stress-response can become more damaging than the stressor itself, especially when the stress is purely psychological.

If you suppress immune function too long and too much, you are now more likely to fall victim to a number of infectious diseases, and be less capable of combating them once you have them.

it is hard to fix one major problem in the body without knocking something else out of balance