Stressed to Kill -- Why Zebras Don't Get Ulcers by Robert M. Sapolsky / Stress, the Aging Brain, and the Mechanisms of Neuron Death by Robert M. Sapolsky

Article excerpt

At an earlier time of my life, before becoming domesticated and deskbound in academia, I spent a fair amount of time carousing with a gang of Hollywood stuntmen. During the day, these maniacs routinely dived in front of speeding trains, leaped off exploding bridges, or rolled burning cars down mountainsides. At night, those who hadn't landed in the hospital gathered at the pub where they laughed, lied, and played marginally sublethal practical jokes on one another, never apparently giving a thought to how close they had come to dying that day or to the hazards of tomorrow. According to Robert Sapolsky, these bouts of boozy and forgetful relaxation were exactly the right way to manage the stress in their lives.

Sapolsky ought to know. He has spent his professional career studying the physiology of stress, specifically how steroid hormones called glucocorticoids, which are released in quantity during stress, affect the brains of rats. But their effect on brains isn't the half of it. In his new book, Why Zebras Don't Get Ulcers, Sapolsky gives us chapter and verse on how chronic stress can disrupt our digestion, damage our stomach lining, stiffen our arteries, stunt our growth, devastate our sex life, cripple our immune system, and, conceivably, hasten our aging rate. You might think that reading three hundred and some pages on this subject would be about as appealing as a dentist with a dull drill, but you would be wrong. The book is a pageturner and is anything but depressing or disheartening.

Stress, defined by physiologists, isn't only the sort of mental anxiety that we commonly associate with a visit by a tax auditor. It is also any exceptional physical demand on the body, such as fleeing from a mugger or saving a child from drowning. For this sort of physical stress, our bodies are superbly designed to respond in an adaptive manner--stress hormones sharpen our senses, dull pain, and redirect energy from immediately nonessential activities, such as digestion or tissue repair, to the appropriate muscles for flight or combat. Sapolsky's point in the title of the book is that while the life of a zebra is dominated by brief physical stresses, the life of a modern human is dominated by chronic mental stress. The same hormones that are so adaptive in short bursts become destructive in longer bouts.

This idea isn't new. Hans Selye, grandfather of stress physiology, developed it nearly fifty years ago. What is new, and what is explained by Sapolsky with witty lucidity, is an appreciation of chronic stress's many destructive mechanisms. For instance, he explains the damaging effects of overexercise by noting how he might try to convince hunter-gatherers from the African savanna that in our culture some presumably sane people actually run twenty-six miles just for exercise. He also gives us an understanding of how stress effects may accumulate later in life and, perhaps most importantly, what psychological and physical factors might minimize the effects of stress. For instance, Sapolsky and colleagues discovered that if newborn rats are gently handled for fifteen minutes per day during the first few weeks of their lives, their glucocorticoid levels are lowered for the remainder of their lives.

One thing that sets Sapolsky apart from most of his colleagues in the field of neuroendocrinology is that he is not locked to his lab bench. Every year he ventures to East Africa to study stress in wild baboons. This is where he hopes to learn something about coping with stress that might be directly applicable to humans. With the prejudice of a field biologist, I think this annual experience gives him a perspective not frequently found in the biomedical community: an appreciation of the adaptive value of physiological traits. He knows that something can be learned by observing how animals cope in nature.

In his study population, male baboons have plenty of food and few predators. Their main source of stress seems to be their involvement in a male dominance hierarchy that seems to be equal parts psychological and physical combat, what you might expect in a tough prison. …