PDF Summary:Why Zebras Don't Get Ulcers, by Robert Sapolsky

Do you feel overworked, exhausted, and constantly stressed? If so, you’re not alone.

In Why Zebras Don’t Get Ulcers, biologist and neuroscientist Robert Sapolsky argues that people today are more stressed than ever before, and it’s causing major physical and mental harm. Fortunately, there are steps you can take to reduce stress in your life and curb the damage caused by chronic stress.

In this guide, we’ll examine the evolution and biology of stress and describe why chronic stress is so harmful physically and psychologically. Then, we’ll look at what you can do to keep stress from causing you too much bodily and mental harm. Throughout the guide, we’ll provide additional context for Sapolsky’s ideas, focusing on the work and research of other scientists and psychologists regarding stress, how it affects us, and how we can manage it.

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Another problem with constant activation of the metabolic stress response is that it increases the amount of fat and glucose circulating in your bloodstream. This can then clog your blood vessels and arteries, which can lead to hypertension. It can also make you more insulin-resistant, which can lead to and exacerbate the effects of diabetes. As stated above, when you’re stressed, glucocorticoids are released to cancel out the insulin in your bloodstream so that you can use the energy from glucose. Do this too often, and you can build up an insulin resistance that characterizes type-2 diabetes.

How Evolution Has Led to Hypertension and Diabetes

Research suggests further evolutionary links between insulin resistance and hypertension beyond stress-related reasons. Throughout most of our evolutionary history, humans have required strong energy storage and salt-retention capabilities. To survive periods of famine or starvation, we needed to be able to store food efficiently. And, to survive the heat and laborious activities, which induce sweat, we needed to be able to retain sodium efficiently. Additionally, the foods available to hunter-gatherers were low in sodium and calories, further adding to our need for these traits.

However, these particular traits we’ve inherited from our ancestors no longer serve a vast majority of people. We live a much more sedentary lifestyle, and we have access to plenty of food with high sodium and caloric content. Because of our different lifestyles, and because our bodies have adapted to store energy and retain sodium, we’re much more likely to develop hypertension, insulin resistance, and type II diabetes.

The All-Encompassing Effects of Chronic Stress

Though we focus on how chronic stress affects your cardiovascular and metabolic health, Sapolsky goes into depth about how stress can be harmful to other systems and parts of the body, leading to a wide variety of ailments and diseases. Here’s a brief overview of the many harms caused by chronic stress:

• Chronic stress can stunt growth in young people.
• Chronic stress can affect reproductive health, decreasing libido and fertility.
• Chronic stress can harm the immune system, leading to autoimmune diseases and immunosuppression.
• Chronic stress can damage the digestive system, causing ulcers and other gastrointestinal issues.
• Chronic stress can affect pain receptors, causing a weakened or heightened tolerance to pain.
• Chronic stress can worsen one’s memory.
• Chronic stress can disrupt sleep and lead to sleep disorders.
• Chronic stress can quicken the aging process.

(Shortform note: The many harmful effects of chronic stress are well-documented. On top of the effects Sapolsky details, chronic stress also affects the musculoskeletal system and the respiratory system. When you’re stressed, your muscles tense up to protect you from pain and injury. If they do this too often, it can lead to headaches, back pain, chronic pain conditions, and even muscular atrophy. Because stress can cause respiratory responses like rapid breathing, chronic stress can make breathing more difficult for those with respiratory diseases like asthma. Stress has even been shown to trigger asthma attacks.)

Stress, Anxiety, and Depression

Chronic stress doesn’t just impact your physical health: It also impacts your mental health. Sapolsky argues that there’s a significant link between stress and mental disorders such as depression and anxiety, which both involve a person inadequately dealing with stress.

Depression

Sapolsky states that there’s a significant link between stress and depression and that chronic stress can be a precursor to a depressive episode. Depression has long been linked to an imbalance or deficiency of neurotransmitters such as norepinephrine, which, as we’ve discussed, makes your body immediately react to a stressor. Furthermore, people suffering from major depression usually have elevated levels of glucocorticoids, a sign of an overactive stress response. Taking all of this into account, here’s a simplified version of how someone falls into a depression:

• First, a significant stressor or series of stressors occurs, causing neurochemical changes that lead to a depressive episode. The more stress you’ve had in the past, especially if at a young age, the more likely these neurochemical changes are to occur.
• Then, glucocorticoids are released that alter the neurochemical processes, helping you recover. Unfortunately, for some people, these recovery processes don’t work as well due to their genetic makeup, making it more likely they’ll fall into a long-term, severe depression.

Sapolsky states that the defining feature of depression is the inability to feel pleasure, also known as anhedonia. People suffering from depression can struggle with feelings of grief or guilt, slow movement or speech, weakened immune systems, lack of libido, and trouble maintaining healthy sleeping and eating habits. These symptoms prevent the sufferer from coping with the stress that caused the depression in the first place.

(Shortform note: The idea that anhedonia is the main symptom of depression is a feature of Western medicine. In the US especially, medical practitioners mainly look for the emotional and cognitive symptoms of depression. In China, the focus is more on physiological symptoms like the inability to concentrate or sleep.)

How Depression Worsens Your Stress Response

Research shows there are specific ways depression can prevent you from effectively handling day-to-day problems. For instance, people with a history of depression are more likely to have a greater decline in their mood when dealing with chronic pain, and pain is more likely to compromise their daily emotional well-being and capacity to cope.

There are two competing hypotheses on why depression affects people’s ability to cope with stress.). The first, known as the “scar hypothesis”, posits that a depressive episode leaves emotional “scars” that leave them more vulnerable to future mood alterations. The second, known as the “trait marker” hypothesis, posits that people who have suffered from depression have pre-existing traits that make them more vulnerable to stress, and these traits persist even after a depressive episode occurs.

Anxiety

Like people with depression, people with anxiety disorders usually have overactive stress responses. The main difference, according to Sapolsky, is that while depressed people have more or less given up on trying to cope with stress, people with anxiety are still able to use coping mechanisms. The problem is that people with anxiety disorders constantly mobilize their stress responses, even when they don’t need to. They’re hypervigilant, overestimating dangers and letting their imaginations lead to a constant state of dread or foreboding. Unsurprisingly, people with anxiety disorders are much more likely to suffer from the many diseases exacerbated by chronic stress.

(Shortform note: Experts note that around 30-40% of people in Western societies will develop an anxiety disorder at some point in their lives. It’s believed that anxious feelings do have a purpose, such as protecting us from dangers and helping us deal with challenges, and it’s improbable that anxiety would be so common if it didn’t help us in some way. However, anxiety becomes a disorder when the sufferer holds inaccurate beliefs that don’t serve them and aren’t based on any objective reality. Furthermore, a major hurdle in tackling anxiety issues is that they cause avoidance behaviors that make it difficult for an anxious person to engage in the activities that would contradict their inaccurate beliefs.)

Though anxiety and depression both involve an overactive stress response, the biological responses differ. With depression, you often see a higher level of glucocorticoids, as the brain tries to recover from a stressor and prepare for the next one. Anxiety, on the other hand, is more often associated with a hyperactive sympathetic stress response (excess epinephrine and norepinephrine), as the brain is constantly on edge and trying to deal with a current stressor.

Through these hormonal and neurochemical responses, we can see how anxiety sometimes leads to depression: Someone constantly tries to cope with a multitude of stressors, showing high sympathetic activation (anxiety). Eventually, if the stress becomes too much to handle, they may give up trying to cope and show high levels of glucocorticoids (depression).

(Shortform note: Another way to frame the difference between anxiety and depression is that depression is associated with a focus on the past while anxiety is focused on the future. This framing is based on the assumption that these negative mental states provide some form of adaptive value to the sufferer: Depression is usually caused by the loss of a goal. So people dwell on the past as a way to come up with a new goal or strategy. Anxiety, on the other hand, is more about dealing with a potential threat to one’s self-preservation. So anxiety entails an obsessive focus on potential future dangers.)

Psychological Factors of Stress

As we’ve explored, the author argues that chronic stress arises because our bodies are responding to constant psychological stressors. But there are outside factors that can impact the degree of stress we experience. Sapolsky identifies five psychological variables that can change the level of stress we feel: 1) the ability to vent frustration, 2) social support, 3) predictability, 4) control, and 5) our perception of whether things are getting better or worse.

Venting Frustration

Sapolsky claims that humans can deal with stress better if they have a way to relieve it. Perhaps you’ve experienced this yourself—maybe you feel less frustrated if you exercise, yell into a pillow, or simply do something you enjoy. Humans can even imagine a way to vent frustration and feel relief. Being able to vent frustration helps distract you from the stressor, but it also reminds you that there is more to life than the stress of your current situation.

(Shortform note: Most stress reduction techniques revolve around finding ways to vent frustration. Here are some more specific ways to vent frustration: Engage with media (such as music, a podcast, or book); take care of your body (by exercising, showering, or eating); go outside; or write about your thoughts or feelings. This last item might give you relief by letting you write about and then imagine releasing your frustration without actually doing anything.)

Social Support

According to Sapolsky, people who feel they have social or communal support are often much less stressed. A number of studies support this effect: When dealing with a relatively small stressor like public speaking or arguing with strangers, people with a supportive friend present show less of a cardiovascular stress response. In women diagnosed with breast cancer, the more social support they have, the lower their cortisol levels. People who are socially isolated, on the other hand, are much more likely to have an overactive sympathetic nervous system.

(Shortform note: Though social support has been shown to reduce the adverse health effects of stress, research suggests that the stress-reducing benefits of social support may not be as strong in marginalized populations. For people living in poverty, social support may not be as helpful as for more affluent populations because there are fewer resources available in poverty-stricken communities and therefore fewer tangible benefits to social support. Additionally, when there are fewer resources available, social support may create more interpersonal conflict, which increases stress.)

Predictability

Furthermore, Sapolsky claims that if you can predict when your next stressor will be, you’ll be less affected by it. This is because when you know that a stressor is coming, you can prepare for it. Additionally, knowing when the stressor won’t happen lets you relax during that time. For example, knowing that at some point in the year you’ll get a sudden migraine is more stressful than knowing which day and at what time it will happen.

(Shortform note: Experts suggest that predictability is especially important for children, whose brains are still developing and who are thus more impacted by stress than adults. Unpredictable environments early in life have been shown to adversely affect the brain’s development and, in some cases, to even affect mental health throughout adulthood. Predictability in a child’s life is so important because it helps set a foundation of trust and care that is vital to healthy relationships and also helps the brain regulate emotions.)

Control

According to Sapolsky, a sense of control over a situation can also alleviate stress. For example, he observes that people are generally more afraid of flying in a plane than driving a car, even though it’s widely known the latter is much more dangerous. This is because when you fly, you cede complete control to the pilot of the plane.

(Shortform note: The stress of air travel doesn’t just stem from a lack of control over steering. As psychologist Sally Augustin explains, when you fly, you’re forced to give up control of your environment. The decisions you have, such as what book to read or whether to open the window, are insignificant compared to the decisions you can no longer make for yourself—you can’t get away from the people sitting right next to you, go out for fresh air, or even use the bathroom at times. All of these lead to a perception that you have no control in your current situation, which is why flying can be so stressful for many people.)

Perception of Things Getting Better or Worse

The same stressor can create drastically different stress reactions depending on whether you feel the situation is improving or worsening, writes Sapolsky. For example, back pain can be stressful, even if it’s mild. But mild back pain is much less stressful for someone who’s been suffering from severe back pain for months because for them, mild back pain is an improvement.

(Shortform note: The way your perception of improvement affects your stress level shows that simply changing how you think about a stressor can change its effect on you. One helpful way to reframe how you think about stress is to embrace the stress in your life. Since stress is inevitable, learning to see stress as something that you can get better at dealing with, and something that can make you a stronger, more capable person, is perhaps more effective than trying to reduce stress.)

How You Can Learn to Better Cope With Stress

Sapolsky contends that you can reduce stress by finding ways to displace frustration, lean on social support, and implement a sense of predictability and control in your life. There are, however, caveats and exceptions to these methods you should be aware of. The key is to find the right strategies and coping mechanisms for certain situations and to figure out which ones work best for you. Let’s look at some of the strategies you can use to reduce psychological stress in your life while keeping in mind some of their caveats.

Exercise as a Way to Vent Frustration

According to Sapolsky, a popular, well-studied, and effective way to reduce stress and vent frustration is to exercise. Remember, the stress response is preparing your muscles to exert energy, so by exercising, you give your body the chance to release that energy. Exercise can also reduce stress by simply taking your mind off the stressful event.

(Shortform note: Using the energy created by a stress response can help you avoid stress response hyperstimulation, in which your body is constantly semi-prepared to respond to stress, and anxiety-induced excess energy, in which you feel you’re too excited or have too much energy. By simply getting rid of some of the energy caused by stress, you may be able to decrease your likelihood of developing an anxiety disorder.)

It’s important to note, however, that exercise only reduces stress if it’s something you want to do. If it’s something you feel like you have to force yourself to do, it may add to your stress levels and worsen your health. Sapolsky points to a study where rats that voluntarily ran on a wheel saw health improvements, but rats that were forced to run saw their health decline.

(Shortform note: A 2016 study reinforces Sapolsky’s claim that forced exercise can be harmful, as it found that mice that were forced to exercise saw increased stress hormones and neuronal damage. It should be noted, however, that the rodents in these experiments are being forced to exercise against their will, which is much different than not wanting to exercise. As a human, you’re rarely if ever forced to exercise against your will. Though you may not want to exercise, it’s still a voluntary decision, so you may still see health benefits. In any case, finding a form of exercise you enjoy is still important as it increases motivation and helps you maintain healthy exercise habits.)

It’s also important to make sure you don’t exercise too much. Too much exercise can be just as bad as or worse for your health than too little exercise.

(Shortform note: Experts say around 150 minutes of moderate physical activity a week is enough to see reduced stress and other health benefits. Too much exercise, however, can lead to an increased chance of injury, exhaustion, and a decline in mental and physical health. Excessive exercise can even be an addiction similar to eating disorders. Like those who practice extreme diets, exercise addicts exercise because they feel a need for control, even though their excessive working out is actually harming them.)

When Predictability Does and Doesn’t Help

We’ve noted that predictability can help reduce stress in humans. Therefore, Sapolsky claims that it can be helpful to make your life more predictable: Make schedules based on various timeframes (daily, weekly, yearly), make a budget to keep track of expenses, look up the weather before going to an outside event, and so on.

Globalization and the Decline of Predictability

Even though people benefit from it, predictability has rapidly declined for many people due to globalization. This could be a significant contributor to rising global stress levels.

When globalization took off in the 1980s and 90s, many organizations discarded standard practices and procedures that made life predictable for the average person—like lifelong job security. To remain competitive in a globalized economy, organizations felt the need to constantly adapt and change alongside it. People across the globe lost stability and predictability, not knowing if their jobs might be discarded, offshored to another part of the world, or made obsolete by rapidly advancing technologies. The rapid changes in the modern world were bound to make life less predictable and thus more stressful.

There are, however, several exceptions to the rule that predictive information reduces stress:

• Getting information about common occurrences doesn’t help much because you’re fairly certain these are going to occur anyway. (It’s not useful to be told that you’ll have to wait in a doctor’s office for the doctor to see you.)
• Getting information about a stressor just before it occurs doesn’t reduce stress because you don’t have enough time to adjust your coping mechanisms. (For example, your hair dresser announces they’re about to cut five inches of your hair and then do.)
• Getting information well before a stressor also doesn’t reduce your stress because you weren’t stressed about it to begin with. (It’s unhelpful to know that in 19 years you’ll have to go to the hospital.)
• Getting information that is too vague might actually increase stress because you don’t know what to do with the information. (Say, you learn that something bad will be announced at work this afternoon.)

(Shortform note: Each of these list items shows ways in which increased predictability doesn’t reduce stress because we can’t do anything useful with the information. Another way we might become stressed is when we receive predictive information that could be useful if acted upon, but we feel that other people aren’t taking the proper precautions. For example, many people fear the effects of climate change and don’t feel others are doing enough to curb those effects. In this way, predictability can actually increase stress—if you know something bad might happen, yet feel no one’s doing anything about it, you’d probably be better off not knowing about it at all.)

When Control Does and Doesn’t Help

According to Sapolsky, a sense of control reduces stress by letting you believe that your actions and decisions have meaning and that you can change a bad outcome or maintain a good one if you work hard enough. In general, people who believe their actions matter, also known as having a strong “internal locus of control,” are better equipped to deal with the psychological stresses of everyday life. For instance, if you are struggling financially, the belief that through determination and effort you can get yourself out of that rut might help you achieve that goal and be less stressed because of it.

A sense of control can only help to a certain extent, however. In general, a sense of control only helps when you believe you can produce positive outcomes. If something bad happens, and you think that outcome was completely within your control, you’ll think about what more you could have done to prevent it, which creates stress.

How to Maintain a Healthy Internal Locus of Control

In The Happiness Advantage, Shawn Achor argues that having an internal locus of control is instrumental to one’s happiness and success. If you have an external locus of control, you blame other people or circumstances for your failures and deny credit for your successes, which leads to an unfulfilling life. Achor also points out that feeling stressed or overwhelmed can disrupt your internal locus of control, causing a vicious cycle of stress and poor decision-making—stress causes you to feel overwhelmed, making it harder to complete the task and leading to even more stress and anxiety.

Sapolsky notes that an internal locus of control can be harmful when dealing with negative outcomes. Here are three tips to avoid feeling stressed by your perception of control over a situation:

• Learn to move on: A sense of control can cause some people to obsess over their role in a negative outcome. When something bad happens, acknowledge what happened, reflect on what you can do differently next time, and then let it go.

• Delegate tasks: People with an internal locus of control may find it hard to share responsibility, but doing so can help alleviate some of the stress when something bad happens.

• Control what you can control: Make note of what you can and can’t control in a situation. This will help you realize that there are things you can’t control and that you simply have to accept them.

How to Best Seek Social Support

Sapolsky claims that having the social support of a community can greatly reduce stress. Even in highly individualized societies, people still long to be a part of something. Therefore, he recommends that to become better at managing stress, you strengthen your current relationships with friends and family and build new ones that are intimate, supportive, and communal.

It’s also important that you give support as well as receive it. Helping others not only strengthens bonds and releases endorphins, but it also gives you a small sense of control in the world—it shows you that through small acts of kindness, you can improve people’s lives and change the world.

The Communal Support of Group Therapy

One form of social support psychologists recommend is group therapy. Group therapy can be extremely beneficial for one’s mental health, especially for those who may not consider themselves a “group person.” Many people are reluctant to join group therapy because, due to a culture that views vulnerability negatively, they’re afraid to talk about their problems in front of a group of people. They may also not like the idea of listening to other people’s problems.

But if you can overcome your reluctance to join a group therapy session, you may see several psychological benefits. With group therapy, you’ll build strong relationships as part of a tight, close-knit community, and you’ll be able to receive and give support, as Sapolsky recommends. Additionally, it can reduce the shame you may have around your negative emotions or feelings because you’re surrounded by others who are going through the same things.