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

“It is never really the case that stress makes you sick, or even increases your risk of being sick. Stress increases your risk of getting diseases that make you sick, or if you have such a disease, stress increases the risk of your defenses being overwhelmed by the disease.”

Sapolsky explores The Biology and Effects of Stress, clarifying that stress, in itself, does not make a person sick. Instead, it creates vulnerability to diseases and their respective symptoms. By highlighting this concept, Sapolsky prevents spreading the sensational idea that stress causes disease. The information is also critical to comprehending more complex ideas, including the variable susceptibility between individuals and the lack of definitive medical answers for how stress results in poor health.

“As the master gland, the brain can experience or think of something stressful and activate components of the stress-response hormonally.”

This statement provides a simplified synopsis of one way in which psychological stressors trigger the sympathetic nervous system. Both thoughts and hormones originate in the brain, which creates an inextricable link between the endocrine and nervous systems. Synopses, such as this, offer condensed, easy-to-digest information, which reflects the intended lay-reader audience (See: Background).

“Faced with similar stressors, whether large or small, two people may also differ in their risk for cardiovascular disease as a function of their personalities […] The bad news is that these personality risk factors are substantial in their impact. But the good news is that something can be done about them.”

Sapolsky alludes to the connection between personality and cardiovascular disease but saves the main discussion for Chapter 15. By introducing the connection and remarking that the effects are strong but alterable, he encourages readers to keep reading. The book is organized in such a way that the scientific discussions are presented first, giving readers the foundational knowledge necessary to fully comprehend the connection between stress and disease, before introducing the potential Strategies for Stress Management and Prevention.

“It is rare today for the grotesquely wealthy to walk around with their fortunes in their pockets, or hoard their wealth as cash stuffed inside mattresses. Instead, surplus wealth is stored elsewhere, in forms more complex than cash: mutual funds, tax-free government bonds, Swiss bank accounts. In the same way, surplus energy is not kept in the body’s form of cash—circulating amino acids, glucose, and fatty acids—but stored in more complex forms.”

The comparison between wealth management and energy storage is an analogy. Sapolsky uses analogies and other creative literary devices to make the scientific information he presents more digestible for the intended lay-reader.

“Personally, all the major rites of passage in my life have been marked by pretty impressive cases of the runs a few days before—my bar mitzvah, going away to college, my doctoral defense, proposing marriage, my wedding. (Finally, here’s that confessional tone obligatory to successful books these days. Now if I can only name some Hollywood starlet with whom I’ve taken diuretics, this may become a bestseller.)”

Multiple literary devices appear in this excerpt. It begins as a personal anecdote, which is intended to humanize Sapolsky and make the text more accessible. The parenthetical remarks swap to humor, as Sapolsky implies that the general public is more interested in drama than in more serious topics, like the non-sensationalized science which predominates the text. 

“Such waxing and waning of stress and of symptoms is particularly difficult to track because most studies are retrospective (they look at people who already have IBS and ask them to identify stressors in their past) rather than prospective (in which people who do not have a disease are followed to see if stress predicts who is going to get it).”

It is common for people to misinterpret the findings of scientific studies as scientific proof. Sapolsky implicitly addresses this issue by describing the issues that arise with retrospective studies. Although some studies on IBS did not find a link between stress and IBS, this does not mean that there is no link. Rather, it is more likely that the studies were flawed. Understanding that findings do not constitute absolute truth is an important factor in science literacy.

“The obvious question to begin this section is, does postnatal stress have lifelong adverse effects on development as well? Of course it can.”

Sapolsky uses hypophora, a type of rhetorical question in which a question is posed and immediately answered, to introduce the topic of postnatal stress. Early-life factors that can impact an individual’s experience of stress form one of the external influences that Sapolsky acknowledges in the text.

“There is a small amount of male sex hormone in the bloodstream of females, even non-hyena females.”

While Sapolsky criticizes gender biases in scientific research, he is still susceptible to it. Sapolsky demonstrates implicit bias by referring to androgen hormones as “male” sex hormones. The statement becomes an oxymoron—if the hormone naturally occurs in a female, then it is not specifically a male hormone.

“Everything bad in human heath now is not caused by stress, nor is it in our power to cure ourselves of all our worst medical nightmares merely by reducing stress and thinking heathy thoughts full of courage and spirit and love. Would that it were so. And shame on those who would profit from selling this view.”

Sapolsky directly criticizes Bernie S. Seigel (See: Key Figures), who claimed that diseases, including cancer, were caused by deviating from God and could be cured by practicing proper mindsets. By shaming those who would profit from sensationalizing the connections between stress and disease, Sapolsky demonstrates his moral values. Sapolsky is careful not to exaggerate or sensationalize the correlations between stress and disease, wishing to avoid blaming individual patients for their illnesses.

“Perhaps the best moral is that when doing science (or perhaps when doing anything at all in a society as judgmental as our own), be very careful and very certain before pronouncing something to be the norm—because at that instant, you have made it supremely difficult to ever again look objectively at an exception to that supposed norm.”

This sentiment reflets modern views toward the concept of normalcy. When a trait is pronounced as normal, those who do not fit within the proposed norm become outliers. This can have consequences within science and within society. By declaring SIDS a result of an enlarged thymus, scientists were delayed in identifying the true cause of the syndrome.

“So we’re at one of those crossroads that makes science look kind of lame. Just like, ‘Stress can increase appetite. And it can decrease it, too,’ we’ve got, ‘Stress can blunt pain perception. But sometimes it does the opposite.’”

Conflicting science results can cause confusion or mistrust of science. Sapolsky attempts to eliminate such confusion by providing detailed explanations and discussing scientific findings within their relevant context. For instance, following this recognition of conflicting results, he clarifies that pain perception is blunted by injury-inducing traumas, like massive burns, but is generally increased by non-injury stressors, like medical anxiety.

“If you learned your introductory neurobiology any time in the last thousand years, one fact that would be hammered in repeatedly is that the adult brain doesn’t make new neurons. In the last decade, it has become clear that this is utterly wrong.”

Sapolsky addresses a significant shift in scientific thinking that encompasses information that many readers have likely been exposed to in the past. In doing so, he implies that scientific facts are subject to change, so people should reserve some skepticism. He also implicitly emphasizes the importance of scientific literacy and staying up-to-date with the latest information.

“We’re not a nocturnal species and if a person works at night or works swing shifts, regardless of how many total hours of sleep she’s getting, it’s going against her biological nature.”

Modern society demands that some individuals sacrifice their health by staying up through the night to provide services for others, reflecting The Implications of Modern Chronic Stress. Studies show that, even when night workers get enough hours of sleep, their sleep quality is reduced because they are not sleeping according to humans’ natural circadian rhythm, or sleep cycle. This demand for modern services demonstrates one way that socioeconomic factors contribute to the prevalence of chronic stress and to stress-related diseases.

“With that rite of passage, he has found the mother lode of psychic energy that fuels our most irrational and violent moments, our most selfish and most altruistic ones, our neurotic dialect of simultaneously mourning and denying, our diets and exercising, our myths of paradise and resurrection.”

Sapolsky posits that much of human behavior is driven by humans’ knowledge of inevitable aging and death. By opening the chapter with this discussion, he demonstrates that aging and the knowledge of death are major stressors. This reflects the catch-22 in the previous chapter on sleep—stress causes sleep deprivation and sleep deprivation causes stress. Similarly, stress speeds the aging process, and the aging process creates stress.

“But when it is our brains that are damaged, when it is our ability to recall old memories or to form new ones that is destroyed, we fear we’ll cease to exist as sentient, unique individuals—the version of aging that haunts us most.”

Sapolsky addresses that most people define themselves by their cognitive abilities—their memories, personalities, etc. By stressing this point, Sapolsky emphasizes the idea that chronic stress might cause damage that quickens the aging of the brain. Throughout much of the first half of the book, Sapolsky avoids sensationalizing his points, but he accentuates the worrisome aspects of stress to make it clear why Strategies for Stress Management and Prevention can be useful.

“People who are socially isolated have overly active sympathetic nervous systems. Given the likelihood that this will lead to higher blood pressure and more platelet aggregation in their blood vessels (remember that from chapter 3?), they are more likely to have heart disease—two to five times as likely, as it turns out. And once they have the heart disease, they are more likely to die at a younger age.”

This cause-and-effect chain of events summarizes the concept of how stress-related diseases develop. People who are socially isolated are more vulnerable to stress; stress causes additional wear-and-tear on the body, leaving it more vulnerable to cardiovascular disease; and cardiovascular disease leaves such individuals more at risk for premature death. Stress does not cause cardiovascular disease or death but creates the conditions, which make people susceptible to such health concerns. This point is a central feature of the book because it describes The Biology and Effects of Stress.

“We differ in the psychological filters through which we perceive the stressors in our world.”

Stress is unique to each person because each person has their own psychological factors through which they perceive stressful events. Stress research is thus inherently complex. The notion that everyone has a unique perspective also implies that people should not be judged for their responses to stressors.

“A key point: many of us tend to think of depressives as people who get the same everyday blahs as you and I, but that for them it just spirals out of control. We may also have the sense, whispered out of earshot, that these are people who just can’t handle normal ups and downs, who are indulging themselves.”

Sapolsky addresses that society often judges individuals with major depression. His use of collective pronouns—“us,” “We,” and “you and I”—prevents him from sounding condescending. It also implies that he, like everyone else, is prone to unfairly judging others. The statements also encourage the reader not to judge others, which is further supported through the phrase “whispered out of earshot,” which suggests that judging others in this way is unethical or shameful.

“There are extremely different ways of looking at the world, and researchers and clinicians from different orientations often don’t have a word to say to one another about their mutual interest in depression.”

Many researchers take a reductive research approach, meaning they break apart complex topics into constituent parts to find underlying causes. Sapolsky takes a more holistic and interdisciplinary approach, using various findings from reductionist studies to compile a broader working model of how depression functions. His method demonstrates the limits of reductionism and the importance of interdisciplinary perspectives.

“Baboons and macaques get distracted during therapy sessions, habitually pulling books off the shelves, for example; they don’t know the days of the week and thus constantly miss appointments; they eat the plants in the waiting room, and so on.”

Sapolsky uses humor to acknowledge that studies on non-human primates are limited. Although primate research can provide insights into the human experience, they are limited because of the researcher’s inability to effectively communicate with non-human species. The humorous tone and imagery briefly break from the technical discussion to incorporate elements of entertainment, reflecting the book’s nature as a popular science text (See: Background).

“A lesson of repressive personality types and their invisible burdens is that, sometimes, it can be enormously stressful to construct a world without stressors.”

Sapolsky uses neutral or compassionate language when discussing personality types that are associated with higher risks of stress-related diseases. He does not place blame on people for exhibiting certain personality traits. In this line, he also encourages readers who may not experience repressive tendencies to understand the perspective of someone who does experience repression.

“If we were nothing but machines of local homeostatic regulation, as we consume more, we would desire less. But instead, our tragedy is that we just become hungrier. More and faster and stronger. ‘Now’ isn’t as good as it used to be, and won’t suffice tomorrow.”

One of The Implications of Modern Chronic Stress is the emergence of increasingly intense synthetic coping mechanisms. Implicit in this concept is the growing unsustainability and the lack of health in westernized lifestyles, which have an ever-increasing demand for sources of pleasure.

“How’s this for an implication of lack of control: one study of the working poor showed that they were less likely to comply with their doctors’ orders to take antihypertensive diuretics (drugs that lower blood pressure by making you urinate) because they weren’t allowed to go to the bathroom at work as often as they needed to when taking the drugs.”

Sapolsky discusses the health consequences of poverty. The working employees in these circumstances are in a catch-22. Their hypertension is likely correlated to the stress of living in poverty conditions, and their poverty conditions make it difficult for them to treat their stress-related diseases, largely because they have a lack of control over their working situations, to the point where they have lost bodily autonomy. Sapolsky is thus always careful to emphasize systemic and structural factors in acknowledging the limitations of Strategies for Stress Management and Prevention.