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

by Robert M. Sapolsky

stress can make us sick

the most upsetting things in life are acute physical crises.

These are extremely stressful events, and they demand immediate physiological adaptations if you are going to live. Your body’s responses are brilliantly adapted for handling this sort of emergency.

An organism can also be plagued by chronic physical challenges.

The body’s stress-responses are reasonably good at handling these sustained disasters.

third category of ways to get upset—psychological and social disruptions.

we humans live well enough and long enough, and are smart enough, to generate all sorts of stressful events purely in our heads.

We can experience wildly strong emotions (provoking our bodies into an accompanying uproar) linked to mere thoughts.*

Antonio Damasio

chess grand masters, during their tournaments, can place metabolic demands on their bodies that begin to approach those of athletes during the peak of a competitive event.*

a person can do nothing more exciting than sign a piece of paper: if she has just signed the order to fire a hated rival after months of plotting and maneuvering, her physiological responses might be shockingly similar to those of a savanna baboon who has just lunged and slashed the face of a competitor.

For the vast majority of beasts on this planet, stress is about a short-term crisis, after which it’s either over with or you’re over with.

A stressor is anything in the outside world that knocks you out of homeostatic balance, and the stress-response is what your body does to reestablish homeostasis.

we can turn on the stress-response by thinking about potential stressors that may throw us out of homeostatic balance far in the future.

Hans Selye.

Allostasis is about the brain coordinating body-wide changes, often including changes in behavior.

Walter Cannon,

He formulated

“fight-or-flight”

It is very rare, however, as we will see, that any of the crucial hormones are actually depleted during even the most sustained of stressors.

the stress-response can become more damaging than the stressor itself

In the face of repeated stressors, we may be able to precariously reattain allostasis, but it doesn’t come cheap, and the efforts to reestablish that balance will eventually wear us down.

PTSD is a constant stressor

allostatic load

cannot turn off the stress-response at the end of a stressful event, the stress-response can eventually become damaging.

Epinephrine is secreted as a result of the actions of the sympathetic nerve endings in your adrenal glands (located just above your kidneys); norepinephrine is secreted by all the other sympathetic nerve endings throughout the body.

parasympathetic component mediates calm, vegetative activities—everything but the four F’s.

Glucocorticoids are steroid hormones.

Epinephrine acts within seconds; glucocorticoids back this activity up over the course of minutes or hours.

Together, glucocorticoids and the secretions of the sympathetic nervous system (epinephrine and norepinephrine) account for a large percentage of what happens in your body during stress. These are the workhorses of the stress-response.

Shelley Taylor of UCLA

Look up her work on stress response in females.

oxytocin is secreted

during stress in females

some glucocorticoid actions prepare

you for the next stressor.

this is c...

for understanding the ease...

anticipatory psychological...

trigger glucocorticoid ...

with there being a particular hormonal “signature” for a

particular stressor.

This is where PTSD messes up the normal response to a stressor and misfires

parasympathetic nervous system begins to slow down your heart via something called the vagus nerve,

As evidence that the atherosclerosis arises from the overactive sympathetic nervous system component of the stress-response, if Kaplan gave the monkeys at risk drugs that prevent sympathetic activity (beta-blockers), they didn’t form plaques.

if you are turning on the sympathetic nervous system all the time, you’re chronically shutting off the parasympathetic. And this makes it harder to slow things down, even during those rare moments when you’re not feeling stressed about something.

you are penalized if you activate the stress-response too often: you wind up expending so much energy that, as a first consequence, you tire more readily—just plain old everyday fatigue.

this could also explain fatigue in PTSD

glucocorticoids make these animals more willing to run mazes looking for food, more willing to press a lever for a food pellet, and so on. The hormone stimulates appetite in humans as well

constant stress from ptsd leads to more glucocorticoids being released leading to appetite increase

really fascinating is that glucocorticoids don’t just stimulate appetite—they stimulate it preferentially for foods that are starchy, sugary, or full of fat—and we reach for the Oreos and not the celery sticks.

Finally, when the stressful event is over, it takes mere seconds for CRH to be cleared from the bloodstream, while it can take hours for glucocorticoids to be cleared.

What this first person is actually experiencing is frequent intermittent stressors. And what’s going on hormonally in that scenario? Frequent bursts of CRH release throughout the day. As a result of the slow speed at which glucocorticoids are cleared from the circulation, elevated glucocorticoid levels are close to nonstop. Guess who’s going to be scarfing up Krispy Kremes all day at work?

So a big reason why most of us become hyperphagic during stress is our westernized human capacity to have intermittent psychological stressors throughout the day. The type of stressor is a big factor.

Elissa Epel of UCSF has shown that the glucocorticoid hypersecreters are the ones most likely to be hyperphagic after stress. Moreover, when given an array of foods to choose from during the post-stress period, they also atypically crave sweets. This is an effect that is specific to stress.

Lots of people eat not just out of nutritional need, but out of emotional need as well. These folks tend both to be overweight and to be stress-eaters.