This article is an excerpt from the Shortform book guide to "Why Zebras Don't Get Ulcers" by Robert Sapolsky. Shortform has the world's best summaries and analyses of books you should be reading.
Like this article? Sign up for a free trial here.
What does chronic stress do to the body? What are the main parts of your body that can be damaged?
According to biologist Robert Sapolsky, modern society has created long-term stressors in our lives, like financial or career concerns. As a result, we now suffer from more chronic stress than ever before, leading to serious mental and physical harm.
Read on to learn about what chronic stress can do to the body, according to Sapolsky.
The Effects of Chronic Stress
In Why Zebras Don’t Get Ulcers, author Robert Sapolsky’s main argument is that the chronic stress humans regularly feel can be extremely damaging to their bodies. So, what does chronic stress do to the body? According to Sapolsky, because dealing with a stressful event can be so intense, and potentially important to one’s survival, the stress response affects virtually every system of the body. So it’s easy to see how chronic stress might be so harmful.
In this article, we’ll look at some of these harmful effects in more detail. We’ll focus on what chronic stress does to two systems in the body: the cardiovascular system and the metabolic system.
Stress and Cardiovascular Health
To explain what chronic stress does to the body, Sapolsky states that the harmful effects of psychological stress are seen most clearly in cardiovascular health. Since stress causes your blood pressure to increase, chronic stress can cause chronically high blood pressure, also known as hypertension. Hypertension can lead to a self-reinforcing cycle: As blood pressure increases, your blood vessels have to work harder to regulate the blood flow and ensure your body is getting adequate oxygen and nutrients. As they work harder, they become stronger and more rigid, and thus more resistant to blood flow. Now there is a constant cycle of increasing vascular resistance and blood flow, driving blood pressure higher and higher.
When blood pressure gets higher, blood returns to your heart at a faster rate, slamming into the wall of your heart. In response, this wall will thicken into what is known as left ventricular hypertrophy, one of the leading predictors of cardiac risk. Similarly, hypertension also causes damage to the blood vessels as the blood moves with more force throughout the body. As this damage occurs, it makes it more likely that plaques will build up at these damaged sites. So chronic stress causes hypertension, which leads to the accumulation of plaques in your bloodstream, and both of these can lead to heart disease, heart attack, and stroke.
|Labile Hypertension and the Effects of Fluctuating Blood Pressure |
In explaining what chronic stress does to the body, Sapolsky argues that the constant raising of blood pressure causes hypertension, which then leads to a variety of cardiovascular health issues. But fluctuations in blood pressure can also cause considerable harm. Labile hypertension differs from hypertension in that it’s defined by extreme variations in your blood pressure over brief periods of time rather than consistently elevated blood pressure. Labile hypertension is usually caused by stress, and it includes many short-term and long-term symptoms.
Several studies emphasize the dangers of fluctuating blood pressure. A 2015 study found that an average blood pressure variation of around 15 mm Hg carried significant cardiovascular risks, including a 46% increased risk of stroke, a 30% increased risk of heart attack or heart disease, and a 58% increased risk of death from any cause. A 2017 study found that dramatic fluctuations in blood pressure may be just as dangerous as consistently high blood pressure. This evidence suggests that the fluctuations in blood pressure caused by stress can be extremely harmful, even if they don’t lead to hypertension.
Stress and Metabolic Health
Another consequence of chronic stress in the body that Sapolsky presents is damage to your metabolic health. During intense physical stressors, your body doesn’t need to digest food and store the energy for later—it needs energy now. To get this energy, the sympathetic nervous system activates, decreasing the secretion of insulin, the hormone responsible for storing energy. Also, glucocorticoids are released to stop nutrients from being transferred to fat cells, which basically cancels out the effects of any insulin left in the bloodstream.
As a result, your body has successfully blocked the energy storage function of your metabolic system, but it also needs to gain access to some of the energy that already is stored. Hormones are then released that transform the more complex proteins stored in fat cells into glucose, which can be converted into energy quickly. After a stressor, the body responds by releasing hormones that increase appetite in order to make up for the energy you just used. This is why many people eat a lot more when stressed.
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.)
———End of Preview———
Like what you just read? Read the rest of the world's best book summary and analysis of Robert Sapolsky's "Why Zebras Don't Get Ulcers" at Shortform.
Here's what you'll find in our full Why Zebras Don't Get Ulcers summary:
- The physical and mental harm chronic stress does to your body
- The steps you can take to reduce stress in your life
- Why you should make your life more predictable