Lessons from the Book Why zebra 🦓 won't get ulcers

Overview

Why Zebras Don’t Get Ulcers (2004) by Robert Sapolsky is a thorough explanation of the impact of chronic stress on the body. It describes the many systems and mechanisms that stress triggers, and the ways that those systems and mechanisms can malfunction. This is the third edition of Why Zebras Don’t Get Ulcers , which was originally published in 1994. This 2004 edition was updated to reflect the state of research in the field as of its publication. Research on some of the physiological problems described in Why Zebras Don’t Get Ulcers has continued to progress since 2004.

The human body can handle a certain amount of stress if it is followed by a recuperative period. This is how wild animals like zebras cope with repeated high-stress crises. This was likewise the case in the early stages of human evolution, but the stresses of modern human life are constant, and are linked to diseases that have become more common today than ever before in history.

The human stress response begins with stimulus. This stimulus could be psychological, but the body treats all stimuli as physical. Stress activates the autonomic nervous system. This includes the sympathetic nervous system, which increases alarm and arousal, and the parasympathetic nervous system, which decreases those responses. During a stress reaction, the brain triggers the pituitary gland, which releases a hormone that tells the adrenal glands to release glucocorticoids. These are chemicals that support increased activity throughout and after the stressful event. The body will also release epinephrine and norepinephrine, which increase and speed up organ activity. After the stress stimulus is gone, the body eliminates the epinephrine and norepinephrine first. Then it eliminates the glucocorticoids while they help the body recover from the stress.

When facing chronic stress, the body never has the chance to fully eliminate the circulating glucocorticoids. As a result, blood pressure rises and does not fall, damaging the blood vessels and heart. The toll on the cardiovascular system can result in atherosclerosis, heart attacks, or strokes.

The digestive system is similarly damaged by repeated exposure to stress. During a stressful event, the body increases energy supplied to the extremities and decreases the energy used by less important muscles. If glucocorticoids disrupt cells’ sensitivity to insulin and increase the amount of energy in the bloodstream, conditions such as diabetes can develop or be exacerbated. Stress responses can cause appetite to be inhibited during the most stressful times and overstimulate it between stressful events. People with high levels of stress tend to gain weight around their abdomens because those fat cells are most sensitive to glucocorticoids. They are susceptible to conditions like irritable bowel syndrome and ulcers, and are more likely to have poor memories and compromised immune systems.

The impact of stress begins early in life, possibly even before birth, because the fetus is exposed to the mother’s levels of glucocorticoids and other stress-related hormones. Extreme stress in childhood can prevent people from growing to adult height, although they generally recover if the stress is eliminated. Engaged maternal contact is closely linked with healthy development and the mitigation of the effects of stress. People who experienced stress early in their lives are more likely to become addicted to a psychostimulant, and once addicted, they are more likely to increase usage when they encounter new stressors. Glucocorticoids are released in large quantities during withdrawal, and additional stress can result in an increased likelihood of relapse.

In adulthood, healthy sexual function relies on a healthy parasympathetic nervous system. Men whose sympathetic nervous systems are constantly activated by stress can experience erectile dysfunction, and women can experience irregular menstrual cycles, decreased libido, and possibly the failure of fertility treatments. Pregnant women can miscarry when exposed to extreme stress.

The body’s stress response has impacts on pain sensitivity, which varies significantly between individuals. In general, stress will decrease sensitivity to pain because the body releases its own opioids into the system. Chronic stress can result in increased sensations of pain as the body’s opioid supplies are depleted or as glucocorticoid release adjusts to constant stressful conditions.

The body responds to psychological stressors in more varied ways than in the way it responds to physical stressors. Reactions are influenced by factors such as whether someone has an outlet for aggression, a social circle, and a sense of control or regularity. Even a positive event can be stressful if one of these factors is lacking. Treating depression as a stress-linked disease and prescribing patients with anti-glucocorticoids can result in alleviated symptoms.

Certain personality traits make an individual more susceptible to chronic stress than others. Glucocorticoid levels are generally low in research subjects who can accurately interpret a situation, respond reasonably and proactively, have an outlet for aggression, and make friends easily. On the other hand, people with anxiety disorders often suffer the consequences of chronic stress, as do people with so-called type-A personalities.

Stressors tend to increase for individuals, human and animal, who live at the bottom of a social hierarchy. Those living in poverty demonstrate the significant impacts of chronic stress in the incidence of the diseases that they are disproportionately likely to contract, particularly in societies with a high degree of inequality between the wealthy and the poor.

Research indicates that the people who handle chronic stress best in old age have had secure, low-stress childhoods; do not smoke or drink to excess; exercise; eat healthfully; and have developed stable social ties. Being well respected and having social power are both strongly correlated with health over time, as is a sense of control over one’s life. Some of these factors cannot be controlled, but people can improve their response to chronic stress with regular, sustained exercise; meditation; planning ahead; developing community ties; practicing coping mechanisms like reframing a situation; and focusing effort on the areas of greatest potential impact.

Key Insights

The brain is the organ that ultimately controls the body’s stress response, through the pituitary gland. It treats physical and mental stressors similarly.

The human body’s stress response starts by increasing awareness and ability to fight or flee, then focuses on long-lasting sources of increased energy. Once the stressor is gone, the body starts the process of recovery.

Glucocorticoids, which are the hormones that the body releases during stress to ensure long-lasting mobilization of energy, impact a wide variety of the body’s systems and are linked to stress-related disorders when they are present in excess or are lacking.

The stress response damages bodily systems when stressors appear in rapid succession because the body cannot fully recover from one stressor before activating the stress response again.

Stress exacerbates medical conditions, causing symptoms that generate more stress. As a result, reproductive health and sleep quality deteriorate when stress is poorly managed.

Processes that evolved to reduce the burden of stress on the body can increase that burden by continuing to act over the long term. Examples of this include the lasting impact of changes to insulin resistance and the suppression of immunity that the stress response triggers to ensure efficiency.

Some disorders linked to chronic stress, such as difficulty forming new memories and lack of growth in childhood, are reversible if stress levels decrease.

Diseases related to chronic stress are more likely to occur in people with controlling personalities, few resources, or a predisposition to addiction.

Stress responses may be linked to disorders such as depression which currently have no clear physiological cause but which appear to be linked to how the body manages stress-response hormones.

People who are resistant to chronic stress-related disorders are more likely to have grown up in stable environments with affectionate parents, less exposure to stressors in the womb, and supportive relationships.

Lifestyle habits such as exercise, a healthy diet, and meditation can reduce the damage done by chronic stress.

Psychological and social practices such as nurturing interpersonal relationships, learning how to interpret events out of one’s control, and learning about uncertainty can prevent extreme responses to stressors.

Important People

Robert Sapolsky is a Stanford University professor specializing in the biology and neurology of stress.

Hans Selye (1907-1982) was an endocrinologist who researched the stress response in organisms.

Walter Cannon (1871-1945) was a Harvard Medical School physiologist who researched the body’s response to stress.

Roger Guillemin and Andrew Schally won the Nobel Prize for Medicine in 1977 for discovering neurotransmitters that initiate the stress response.

Author’s Style

Why Zebras Don’t Get Ulcers is an in-depth consideration of a complex and oft-misunderstood science. Sapolsky conveys new developments and emerging theories with clarity and a gradual approach that does not overwhelm the reader. The narrative contains technical language, but all terms are introduced on first use and the significant concepts are regularly reiterated. Comprehension relies on only a few vocabulary terms.

Sapolsky writes in a light and friendly tone. He addresses the reader directly and frequently describes what he imagines the reader is thinking as the book progresses. He makes use of humor and accompanies descriptions of complicated biological processes with similes and metaphors that are consistent and clear. His writing expresses his own excitement about the subject of chronic stress.

The author briefly describes experiences as a father, researcher, and observer in the field of stress sciences throughout the narrative. Sapolsky includes stories and examples that illustrate the scientific method and the challenges of drawing conclusions from laboratory studies on non-human subjects. He discusses the methodology of those studies in detail and makes a clear distinction between the conclusions of the study and his interpretation of what those conclusions mean.

Asterisks mark the location of endnotes throughout the narrative. The endnotes generally provide historical context and extra detail. Sources and recommended reading are included, but they are not linked directly to the portions of the book that quote or use them by way of citations.

Author’s Perspective

Robert Sapolsky is a neuroendocrinologist who teaches in the departments of biological sciences, neurological sciences, and neurosurgery at Stanford University. He conducts research at the Institute of Primate Research at the National Museum of Kenya. Sapolsky received a MacArthur Fellowship grant in 1987, and is recipient of the Alfred P. Sloan Fellowship. He has written several best-selling books for a general audience, including The Trouble With Testosterone (1998) and A Primate’s Memoir (2002). Sapolsky has also written for the New York Times, Wired , and Scientific American .

Sapolsky addresses many politically and socially sensitive subjects throughout Why Zebras Don’t Get Ulcers . He describes the impact of poverty and class inequality, controversial diagnoses and treatments, sexual dysfunction, Freudian psychology, and spirituality. He spares no details when discussing the impact of stress on sex. He also expresses his awareness of the political and social implications of his own writing, acknowledging the perspective from which he writes and the biases that might reveal.

Intended Audience

Why Zebras Don’t Get Ulcers is a dense book about a highly specialized subject. Its narrative will have special appeal to anyone who feels the pressure of chronic stress or suspects that stress responses are connected to poorly understood conditions. Because Sapolsky’s explanations of specialized subjects move from basic foundations to greater detail and complexity, readers with a general understanding of human anatomy and health will be able to follow them. However, readers will not find specific advice, instructions, or other guidelines for reducing or coping with stress, as they would in a self-help text. Sapolsky prefers to deliver general information about the factors associated with better stress management, but he acknowledges that many of the factors are outside of any individual’s control.