View source | |
# 2022-01-04 - Why Zebras Don't Get Ulcers by Robert Spolsky | |
When i took a workshop on TRE (Trauma/Tension Releasing Exercises), | |
Why Zebras Don't Get Ulcers was highly recommended reading. A family | |
member loaned me the book and i finally got around to reading it. I | |
really enjoyed the level of detail in this book, and yet it was quite | |
accessible. What follows are excerpts that i found interesting while | |
reading the book. | |
# Preface | |
There has been a revolution in medicine concerning how we think about | |
the diseases that now afflict us. It involves recognizing the | |
interactions between the body and the mind, the ways in which | |
emotions and personality can have tremendous impact on the | |
functioning of virtually every cell in the body. ... the critical | |
notion that you cannot really understand a disease in vacuo, but | |
rather only in the context of the person suffering from that disease. | |
# Chapter 1 | |
Kind of stress: | |
* acute physical crises: the body's responses are brilliantly | |
adapted to this | |
* chronic physical challenges: the body's stress-responses are | |
reasonably good at handling these sustained disasters | |
* psychological and social disruptions: these are recent | |
inventions, in the evolutionary timescale | |
A large body of evidence suggests that stress-related disease | |
emerges, predominantly, out of the fact that we so often activate a | |
physiological system that has evolved for responding to acute | |
physical emergencies, but we turn it on for months on end... | |
In the 1930s, Hans Selye formalized the concept of stress with two | |
ideas: | |
* The body has a surprisingly similar set of responses to a broad | |
array of stressors. | |
* If stressors go on for too long, they can make you sick. | |
... a stressor can be defined as anything that throws your body out | |
of allostatic balance and the stress-response is your body's attempt | |
to restore allostasis. For us vertebrates, the core of the | |
stress-response is built around the fact that your muscles are going | |
to work like crazy. One of the hallmarks of the stress-response is | |
the rapid mobilization of energy... | |
If your body has mobilized all that glucose, it also needs to deliver | |
it to the critical muscles as rapidly as possible. Heart rate, blood | |
pressure, and breathing rate increase... digestion is inhibited... | |
growth and tissue repair is curtailed, sexual drive decreases, | |
immunity is inhibited, pain becomes blunted, memory and senses | |
sharpen. | |
With prolonged stress, diseases emerge... The body spends so much on | |
the defense budget that it neglects education, health care, and | |
social services. With sufficient activation, the stress response can | |
become more damaging to the stressor itself. The same systems of the | |
brain that function more cleverly during stress can also be damaged | |
by one class of hormones secreted for stress. | |
It isn't 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. | |
# Chapter 2 | |
ANS: autonomic nervous system | |
Half of this system is activated in response to stress, half is | |
suppressed. | |
The half of the ANS that is turned on is called the sympathetic | |
nervous system. This is the part that activates goosebumps. | |
UK: adrenaline | |
US: epinephrine | |
UK: noradrenaline | |
US: norepinephrine | |
The parasympathetic component mediates calm, vegetative activities: | |
sleep, growth, energy storage, drowsiness after a large meal. | |
Sympathetic: speeds up heart, divers blood to the muscles | |
Parasympathetic: does the opposite | |
the parts of the brain that activate on of the two branches typically | |
inhibit the other. | |
neurotransmitters go from cell to adjacent cell. hormones go through | |
the blood stream. | |
norepinephrine can be either a neurotransmitter or a hormone. | |
the pituitary gland contains a whole array of hormones that run the | |
show... it regulates what all the other glands do. In 1944, the | |
physiologist Geoffrey Harris proposed that the brain was also a | |
hormonal gland, that it released hormones that traveled to the | |
pituitary and directed the pituitary's actions. Specifically, the | |
hypothalamus. | |
As the master gland, the brain can experience or think of something | |
stressful and activate components of the stress-response hormonally. | |
Some of the hypothalamus-pituitary-peripheral glands are activated | |
during stress, some inhibited. | |
Another important class of hormones in the response to stress are | |
called glucocorticoids. Glucocorticoids are steroid hormones. | |
Steroid is used to describe the general chemical structure of five | |
classes of hormones: | |
* androgens | |
* estrogens | |
* progestins | |
* mineralocorticoids | |
* glucocorticoids | |
Secreted by the adrenal gland, glucocorticoids often act in ways | |
similar to epinephrine. Epinephrine acts within seconds; | |
glucocorticoids back this activity up over the course of minutes or | |
hours. | |
When something stressful happens or you think stressful thoughts, the | |
hypothalamus secretes an array of hormones that gets the ball | |
rolling. The principal such releaser is called CRH (corticotropin | |
releasing hormone)... Within fifteen seconds or so, CRH triggers the | |
pituitary to release the hormone ACTH (also known as corticotropin). | |
After ACTH is released into the bloodstream, it reaches the adrenal | |
gland and, within a few minutes, triggers glucocorticoid release. | |
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. | |
[male and female stress response differs. In addition to fight or | |
flight, there is also tend and befriend. Oxytocin is secreted during | |
stress in females.] | |
Sympathetic arousal is a relative marker of anxiety and vigilance, | |
while heavy secretion of glucocorticoids is more a marker of | |
depression. | |
# Chapter 3 | |
Basically your heart is a pump and your blood vessels are hoses. The | |
cardiovascular stress-response essentially consists of making them | |
work harder for a while, and if you do that on a regular basis, they | |
will wear out... | |
The first step in the road to stress-related disease is developing | |
hypertension, chronically elevated blood pressure. | |
... after controlling for age, having left ventricular hypertrophy is | |
the single best predictor of cardiac risk. | |
The branch points in the [blood] vessel wall where bifurcation occurs | |
bear the brunt of the fluid pressure slamming into them. Thus, a | |
simple rule: when you increase the force with which the fluid is | |
moving through the system, turbulence increases and those outposts of | |
wall are more likely to get damaged. | |
With the chronic increase in blood pressure that accompanies repeated | |
stress, damage begins to occur at the branch points in arteries | |
throughout the body. The smooth inner lining of the vessel begins to | |
tear or form little craters of damage. Once this layer is damaged, | |
you get an inflammatory response--cells of the immune system that | |
mediate inflammation aggregate around the injured site. Moreover, | |
cells full of fatty nutrients, called foam cells, begin to form there | |
too. In addition, during stress the sympathetic nervous system makes | |
your blood more viscous. Specifically, epinephrine makes circulating | |
platelets (a type of blood cell that promotes clotting) more likely | |
to clump together, and these clumped platelets can get gummed up in | |
these aggregates as well. As we'll see in the next chapter, during | |
stress you're mobilizing energy into the bloodstream, including fat, | |
glucose, and the "bad" type of cholesterol, and these can add to the | |
aggregate. All sorts of fibrous gunk builds up there, too. You've | |
now made yourself an atherosclerotic plaque. | |
Therefore, stress can promote plaque formation by increasing the odds | |
of blood vessels being damaged and inflamed, and by increasing the | |
likelihood that circulating crud... sticks to those inflamed injury | |
sites. In the last few years, it is becoming clear that the amount | |
of damaged inflamed blood vessels is a better predictor of | |
cardiovascular trouble than is the amount of circulating crud. How | |
can you measure the amount of inflammatory damage? A great marker is | |
turning out to be something called C-reactive protein (CRP). CRP is | |
turning out to be a much better predictor of cardiovascular disease | |
risk than cholesterol, even years in advance of disease onset. As a | |
result, CRP has suddenly become quite trendy in medicine... | |
But we're not done. Once you've formed those plaques, continued | |
stress can get you in trouble another way. Again, increase stress | |
and increase blood pressure, and, as blood moves with enough force, | |
increase the chances of tearing that plaque loose, rupturing it. | |
[This can] form what is called a thrombus, and that mobile hairball | |
can now lodge in a much smaller blood vessel, clogging it completely. | |
Clog up a coronary artery and you've got a myocardial infarct, a | |
heart attack (and this thrombus route accounts for the vast majority | |
of heart attacks). Clog up a blood vessel in the brain and you have | |
a brain infarct (a stroke). | |
But there's more bad news. If chronic stress has made a mess of your | |
blood vessels, each individual new stressor is even more damaging, | |
for an additional insidious reason. This has to do with myocardial | |
ischema, a condition that arises when the arteries feeding your heart | |
have become sufficiently clogged that your heart itself is partially | |
deprived of blood flow and thus Oxygen and glucose. [In a healthy | |
person the body has mechanisms to make sure the stress response does | |
not starve the heart.[ But if you encounter an acute stressor with a | |
heart that has been suffering from chronic myocardial ischema, you're | |
in trouble. The coronary arteries, instead of vasodilating in | |
response to the sympathetic nervous system, vasoconstrict. | |
But one of the most striking and best know features of heart disease | |
is how often that cardiac catastrophe hits during a stressor. The | |
phenomenon is quite well documented. Embedded in the list of | |
categories of precipitants of sudden cardiac death is a particularly | |
interesting one: triumph or extreme joy. Extreme anger and extreme | |
joy have different effects on [various body systems]; but with regard | |
to the cardiovascular system, they have fairly similar effects. | |
# Chapter 4 | |
The hormone that stimulates the transport and storage of these | |
building blocks into target cells is insulin. Insulin is this | |
optimistic hormone that plans for your metabolic future. Eat a huge | |
meal and insulin pours out of the pancreas into the bloodstream, | |
stimulates the transport of fatty acids into fat cells, [and] | |
stimulates glycogen and protein synthesis. We even secrete insulin | |
when we are ABOUT to fill our bloodstream with all those nutritive | |
building blocks: if you eat dinner each day at six o'clock, by five | |
forty-five you're already secreting insulin in anticipation of the | |
rising glucose levels in your bloodstream. Logically, is is the | |
parasympathetic nervous system that stimulates the anticipatory | |
secretion... | |
Stress response: | |
* Turn up the activity of the sympathetic nervous system, turn down | |
the parasympathetic nervous system, and down goes insulin secretion. | |
* Secrete glucocorticoids, which block the transport of nutrients | |
into fat cells. This counteracts the effects of any insulin still | |
floating around. | |
* Your body reverses all the storage steps through the release of | |
the stress hormones: glucocorticoids, glucagon, epinephrine, | |
norepinephrine. These cause triglycerides to be broken down in the | |
fat cells and, as a result, free fatty acids and glycerol pour into | |
the circulatory system. The same hormones trigger the degradation | |
of glycogen to glucose in cells throughout the body, and glucose is | |
then flushed into the bloodstream. These hormones also cause | |
protein in non-exercising muscles to be converted back into | |
individual amino acids. | |
* Your body shunts the circulating amino acids into the liver, | |
where they are converted to glucose. The liver can also generate | |
new glucose, a process called gluconeogenesis... | |
In effect, you are penalized if you activate the stress-response to | |
often: you wind up expending so much energy that, as a first | |
consequence, you tire more readily--just plain old everyday fatigue. | |
As a second consequence, your muscles can waste away, although this | |
rarely happens to a significant degree. | |
Finally, [this puts more crud and LDL cholesterol into your | |
bloodstream, which increases risks of cardiovascular disease.] | |
Stress, including psychological stress, can wreak havoc with | |
metabolism control in a juvenile diabetic. [Stress is also involved | |
in increased risk of developing juvenile diabetes.] Therefore, this | |
is a population in which successful stress management is critical. | |
[Adult onset diabetes, type 2, insulin resistant diabetes involves] | |
the failure of cells to respond to insulin. | |
And if the adult-onset diabetes goes on for a while, an additional, | |
miserable development can occur. Your body has become insulin | |
resistant. Your pancreas responds by secreting even more insulin | |
than usual. You're still resistant. So the pancreas secretes even | |
more. Back and forth, your pancreas pumping out ever higher levels | |
of insulin, trying to be heard. Eventually, this burns out the | |
insulin-secreting cells in the pancreas, actually destroying them. | |
[Thus type 2 diabetes can turn into type 1 diabetes.] | |
What should be obvious over the last two chapters is that your | |
metabolic and cardiovascular systems are intimately interconnected. | |
Metabolic syndrome (also known as Syndrome X) is a new term | |
recognizing this interconnection. | |
Take more than a thousand study subjects, all over age 70, none of | |
whom are certifiably sick--that is to say, where none of these | |
[individual] measures are technically abnormal. Now, see how they're | |
doing on all those Metabolic syndrome measures [put together]. Throw | |
in some other measures as well... Combine the insights of these | |
measures mathematically and, collectively, this information was | |
significantly predictive of who was going to have heart disease, a | |
decline in cognitive or physical functioning, and morality, far more | |
predictive than subsets of those variables alone. | |
# Chapter 5 | |
The official numbers are that stress makes about two thirds of people | |
hyperphagic (eating more) and the rest hypophagic. | |
The confusing issue is that one of the critical hormones of the | |
stress-response stimulates appetite, while another inhibits it. CRH | |
inhibits appetite. | |
What is really fascinating is that glucocorticoids don't just | |
stimulate appetite--they stimulate it preferentially for foods that | |
are starchy, sugary, or full of fat. | |
CRH makes its effects felt within seconds, while glucocorticoids take | |
minutes to hours to exert their actions. 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. | |
Glucocorticoids not only increase appetite but, as an additional | |
means to recover from the stress response, also increase the storage | |
of the ingested food. | |
It turns out that when glucocorticoids stimulate fat deposition, they | |
do it preferentially in the abdomen... | |
... lots of fat is a predictor for Syndrome X. But it turns out that | |
a large WHR (waist-hip ratio) is an even better predictor of trouble | |
than being overweight [alone] is. | |
run-of-the-mill mammals, including us, expend 10-20 percent of their | |
energy on digestion. | |
["organic" gastro-intestinal disorders are caused by physical damage, | |
i.e. ulcers] | |
["functional" gastro-intestinal disorders happen even though all the | |
organs are in good shape.] | |
The most common functional gastro-intestinal disorder is irritable | |
bowel syndrome (IBS), which involves abdominal pain (particularly | |
just after a meal) that is relieved by defecating... | |
So ongoing stress can be closely associated with IBS. Interestingly, | |
traumatic stress early in life (abuse, for example) greatly increases | |
the risk of IBS in adulthood. | |
ulcers originating in the stomach or in the organs immediately | |
bordering it are termed peptic ulcers. The ones within the stomach | |
are called gastric ulcers; those a bit higher up than the stomach are | |
esophageal, and those at the border of the stomach and the intestines | |
are duodenal (the most common of peptic ulcers). | |
And this bacterium [Heliobacter pylori] probably has a lot to do with | |
85 to 100 percent of ulcers in Western populations (as well as with | |
stomach cancer). Nearly 100 percent of people in the developing | |
world are infected with Heliobacter--it is probably the most common | |
chronic bacterial infection in humans. | |
The trouble is that one bacterium can't be the whole story. For | |
starters, up to 15 percent of duodenal ulcers form in people who | |
aren't infected with Heliobacter, or with any other known bacterium | |
related to it. More damning, only about 10 percent of the people | |
infected with the bacteria get ulcers. It's got to be Heliobacter | |
pylori plus something else. | |
An analysis of the entire literature shows that somewhere between 30 | |
to 65 percent of peptic ulcers have psychosocial factors (i.e., | |
stress) involved. ... after you control for [lifestyle risk factors | |
such as drinking], stress itself still causes a two to threefold | |
increase in the risk of an ulcer. | |
# Chapter 7 | |
Of all the hormones that inhibit the reproductive system during | |
stress, prolactin is probably the most interesting. It is extremely | |
powerful and versatile; if you don't want to ovulate, this is the | |
hormone to have lots of in your bloodstream. It not only plays a | |
major role in the suppression of reproduction during stress and | |
exercise, but it also is the main reason that breast feeding is such | |
an effective form of birth control. | |
Breast feeding causes prolactin secretion. There is a reflex loop | |
that goes straight from the nipples to the hypothalamus. If there is | |
nipple stimulation for any reason (in males as well as females), the | |
hypothalamus signals the pituitary to secrete prolactin. And as we | |
now know, prolactin in sufficient quantities causes reproduction to | |
cease. | |
The problem with nursing as a contraceptive is how it is done in | |
Western societies. During the six months or so that she | |
breast-feeds, the average mother in the West allows perhaps half a | |
dozen periods of nursing a day, each for 30 to 60 minutes. Each time | |
she nurses, prolactin levels go up in the bloodstream within seconds, | |
and at the end of the feeding, prolactin settles back to pre-nursing | |
levels fairly quickly. | |
This is not how most women on earth nurse. A prime example emerged a | |
few years ago in a study of hunter-gatherer Bushmen in the Kalahari | |
Desert of southern Africa. Bushmen males and females have plenty of | |
intercourse, and no one uses contraceptives, but the women have a | |
child only about every four years. | |
Instead, the lengthy interval is probably due to their nursing | |
pattern. This was discovered by a pair of scientists, Melvin Konner | |
and Carol Worthman. When a hunter-gatherer woman gives birth, she | |
begins to breast-feed her child for a minute or two approximately | |
every fifteen minutes. Around the clock. For the next three years. | |
The young child is carried in a sling so he [or she] can nurse easily | |
and frequently. At night, he [or she] sleeps his [or her] mother and | |
will nurse every so often without even waking her. Once the kid can | |
walk, he'll [or she'll] come running in from play every hour or so to | |
nurse for a minute. | |
When you breast-feed in this way, the endocrine story is very | |
different. At the first nursing period, prolactin levels rise. And | |
with the frequency and timing of the thousands of subsequent | |
nursings, prolactin stays high for years. Estrogen and progesterone | |
levels are suppressed, and you don't ovulate. | |
# Chapter 8 | |
In order to sound immune alarms throughout this far-flung system, | |
blood-borne chemical messengers that communicate between different | |
cell types, called cytokines, have evolved. | |
Such acquired immunity is a pretty fancy invention, and it is found | |
only in vertebrates. But we also contain a simpler, more ancient | |
branch of the immune system, one shared with species as distant as | |
insects, called innate immunity. [This involves generic antibodies | |
that attack any microbe.] | |
In chapter 1 ... I suggested that during stress it is logical for the | |
body to shut down long-term building projects in order to divert | |
energy for more immediate needs--this inhibition includes the immune | |
system, which, while fabulous at spotting a tumor that will kill you | |
in six months or making antibodies that will help you in a week, is | |
not vital in the next few moments' emergency. However, [the immune | |
system is not merely put on hold.] Instead, stress causes the active | |
expenditure of energy in order to disassemble the preexisting immune | |
system... you're PAYING, energetically, to take apart the immune | |
system. | |
During infections, the immune system releases the chemical messenger | |
interleukia-1, which among other activities stimulates the | |
hypothalamus to increase CRH. CRH stimulates the pituitary gland to | |
release ACTH, which then causes adrenal release of glucocorticoids. | |
These in turn suppress the immune system. In other words, under some | |
circumstances, the immune system will ask the body to secrete | |
hormones that will ultimately suppress the immune system. It is | |
probably not just an accident. | |
It turns out that during the first few minutes (say, up to about 30) | |
after the onset of a stressor, you don't uniformly suppress | |
immunity--you enhance many aspects of it. | |
[But] when stress goes on longer... By the one-hour mark, more | |
sustained glucocorticoid and sympathetic activation begins to have | |
the opposite effect, namely, suppressing immunity. | |
... if you have a stressor that goes on for too long, an adaptive | |
decline back to baseline can overshoot and you get into trouble. | |
Thus, early on during exposure to a stressor, glucocorticoids and | |
other stress-responsive hormones transiently activate the immune | |
system, enhancing immune defenses, sharpening them, [and] | |
redistributing immune cells to the scenes of infectious battle. | |
Because of the dangers of the system's overshooting into | |
autoimmunity, more prolonged glucocorticoid exposure begins to | |
reverse these effects, bringing the system back to baseline. And | |
during the pathological scenario of truly major, sustained stressors, | |
immunity is suppressed below baseline. | |
Insofar as autoimmune diseases involve overactivation of the immune | |
system, the most time-honored treatment is to put people "on | |
steroids"--to give them massive amounts of glucocorticoids [stress | |
hormones--to suppress the immune system.] | |
Stress is among the most reliable, if not the most reliable, factor | |
to worsen autoimmune diseases. | |
... it seems as if numerous transient stressors increase the risk of | |
autoimmunity--for some reason, repeated ups and downs ratchet the | |
system upward, biasing it toward autoimmunity. [Also, having | |
inadequate "cool-down" after each upswing] pushes the immune system | |
upward into autoimmunity. | |
The system apparently did not evolve for dealing with numerous | |
repetitions of coordinating the various on-and-off switches, and | |
ultimately something uncoordinated occurs, increasing the risk that | |
the system becomes autoimmune. | |
Herpes DNA contains a stretch that is sensitive to elevated | |
glucocorticoid signals, and when levels are up, that DNA sensor | |
activates the genes involved in coming out of latency. Epstein-Barr | |
and varicella-zoster contain this glucocorticoid-sensitive stretch as | |
well. | |
[Stress accelerates tumor growth in lab animals.] Substitute | |
glucocorticoids [for the stressors] and tumor growth is accelerated | |
as well. | |
And these glucocorticoids directly influence tumor biology through | |
both immune and non-immune realms. The immune system contains a | |
specialized class of cells (most notably, natural killer cells) that | |
prevent the spread of tumors. Stress suppresses the numbers of | |
circulating natural killer cells... Once a tumor starts growing, it | |
needs enormous amounts of energy, and one of the first things that | |
tumors do is send a signal to the nearest blood vessel to grow a bush | |
of capillaries into the tumor. [angiogenesis] Glucocorticoids at | |
the concentration generated during stress aid angiogenesis. | |
When you rely on the rare prospective studies, there turns out not to | |
be good evidence for a stress-cancer link. | |
The cancer-prone personality, we're told, is one of | |
repression--emotions held inside, particularly those of anger. This | |
is a picture of an introverted, respectful individual with a strong | |
desire to please--conforming and compliant. Hold those emotions | |
inside and it increases the likelihood that out will come cancer, | |
according to this view. | |
# Chapter 9 | |
Pain is useful to the extend that it motivates us to modify our | |
behavior in order to reduce whatever insult is causing the pain, | |
because invariably that insult is damaging our tissues. Pain is | |
useless and debilitating, however, when it is telling us that there | |
is something dreadfully wrong that we can do nothing about. | |
Some pain receptors carry only information about pain (for example, | |
the ones corresponding to cuts); others carry information about both | |
pain and everyday sensations. | |
A striking aspect of the pain system is how readily it can be | |
modulated by other factors. The strength of a pain signal, for | |
example, can depend on what other sensory information is funneled | |
through the spine at the same time. This, it turns out, is why it | |
feels so great to have a massage when you have sore muscles. | |
The brain's interpretation of pain can be extremely subjective. This | |
is because the brain is not a mindless pain-ometer, simply measuring | |
units of ouchiness. But most of what the brain's responses to pain | |
are about is generating emotional responses and giving contextual | |
interpretations about the pain. | |
How much pain you feel and how unpleasant that pain feels, can be two | |
separate things. | |
Those more emotive parts of the brain not only can alter how you | |
respond to pain information coming up the spinal cord; those areas of | |
the brain can alter how the spinal cord [itself] responds to pain | |
information. | |
Soon they found exactly what they were looking for: endogenous | |
compounds with chemical structures reminiscent of the opiate drugs. | |
They turned out to come in three different classes: ekephalins, | |
dynorphins, and the most famous of them all, endorphins (a | |
contraction for "endogenous morphines"). (Opiate refers to | |
analgesics not normally made by the body... Opioid refers to those | |
made by the body itself.) | |
Furthermore, scientists noted that Chinese veterinarians used | |
acupuncture to do surgery on animals, thereby refuting the argument | |
that the painkilling characteristic was one big placebo effect... | |
Acupuncture stimulates the release of large quantities of endogenous | |
opioids, for reasons no one really understands. | |
Endogenous opioids turn out to be relevant to explaining placebos as | |
well. | |
In 1977 Roger Guillemin demonstrated that stress triggers the release | |
of one type of endorphin, beta-endorphin, from the pituitary gland. | |
[On the other hand, stress-induced hyperalgesia causes pain to seem | |
worse. Hyperalgesia] has nothing to do with pain receptors or the | |
spinal cord. Instead, it involves more emotional reactivity to pain, | |
interpreting the same sensation as more unpleasant. | |
Stress-induced analgesia does not go on forever, and the best | |
evidence ascribes this to depletion of opioids. You are not | |
permanently out... but it takes a while for supply to catch up with | |
demand. [The pain will return.] | |
# Chapter 10 | |
Stress can enhance memory. Stress can disrupt memory. Short-term | |
stressors of mild to moderate severity enhance cognition, while major | |
or prolonged stressors are disruptive. | |
[Types of memory: short-term, long-term, and remote memory i.e. early | |
childhood memories.] | |
Explicit (also known as declarative) memory concerns facts and | |
events, along with your conscious awareness of knowing them... | |
Implicit memories can be used even without having to think | |
consciously of them. | |
Implicit procedural memories are about skills and habits, about | |
knowing how to DO things. | |
Memories can be transferred between explicit and implicit forms of | |
storage. | |
Memory can be dramatically disrupted if you force something that's | |
implicit into the explicit channels. | |
"muscle memory" is implicit procedural memory. | |
The sympathetic nervous system pulls this off [during stress] by | |
indirectly arousing the hippocampus into a more alert, activated | |
state, facilitating memory formation. This involves the amygdala. | |
[Memory formation uses a lot of energy.] The sympathetic nervous | |
system helps by mobilizing glucose into the bloodstream and | |
increasing the force with which blood is being pumped into the brain. | |
In addition, a mild elevation in glucocorticoid levels helps memory | |
as well. This occurs in the hippocampus, where those moderately | |
elevated glucocorticoid levels facilitate long-term potentiation. | |
Finally, there are some obscure mechanisms by which moderate, | |
short-term stress makes your sensory receptors more sensitive. | |
... just a few days of high doses of synthetic glucocorticoids | |
impairs explicit memory in healthy volunteers. | |
It turns out that the hippocampus has large amounts of two different | |
types of receptors for glucocorticoids. Critically, the hormone is | |
about ten times better at binding to one of the receptors (thus | |
termed a "high-affinity" receptor) than the other. What that means | |
is that if glucocorticoid levels rise only a little bit, most of the | |
hormone effect in the hippocampus will be mediated by that | |
high-affinity receptor. In contrast, it is not until you are dealing | |
with a major stressor that the hormone activates a lot of the | |
"low-affinity" receptor. And, logically, it turns out that | |
activation of the high-affinity receptor enhances long-term | |
potentiation, while activation of the low-affinity one does the | |
opposite. | |
... the amygdala plays a central role in the types of emotional | |
memories involved in anxiety. Activation of [the amygdala during | |
major stressors] seems to be a prerequisite for stress to disrupt | |
hippocampal functionality. | |
Actually, the evidence for new neurons in the adult brain [adult | |
neurogenesis] was first reported in the 1960s by a handful of | |
heretics who were generally ignored or hounded out of science. The | |
field has finally caught up with them. | |
The hippocampus is one of only two sites in the brain where these new | |
neurons originate. The other region supplies new neurons to the | |
olfactory system; for some strange reason, neurons that process odors | |
constantly die off and have to be replaced. It turns out that there | |
is a huge burst in the production of those new olfactory neurons | |
early during pregnancy. They are fully on line just around the time | |
of birth, and the scientists who discovered this speculated that | |
these new olfactory neurons are tagged for the task of imprinting | |
forever on the smell of your offspring... | |
Finally, there is now evidence that truly prolonged exposure to | |
stress or glucocorticoids can actually kill hippocampal neurons. | |
# Chapter 11 | |
Not getting enough sleep is a stressor; being stressed makes it | |
harder to sleep. Yep, we've got a dread vicious cycle on our hands. | |
Sleep is not a monolithic process... Instead, there are different | |
types of sleep--shallow (also known as stages 1 and 2) sleep, where | |
you are easily wakened. Deep sleep (also known as stages 3 and 4, or | |
"slow wave sleep"). Rapid Eye Movement (REM) sleep, where the | |
puppy's paws flutter and our eyes dart around and dreams happen. | |
There are not only these different stages, but a structure, an | |
architecture to them. You start off shallow, gradually sleep your | |
way down to slow wave sleep, followed by REM, then back up again, and | |
then repeat the whole cycle about every 90 minutes... | |
[During slow wave sleep, parts of the brain slow down.] | |
Interestingly, regions involved in the consolidation and retrieval of | |
memories don't have much of a decrease in metabolism. ... deep slow | |
wave sleep is when energy restoration occurs. | |
Overall, there's an increase in activity [during REM sleep]. The | |
frontal cortex is the nearest thing we have to a superego. The | |
frontal cortex does all this disciplining you by inhibiting that | |
frothy, emotional limbic system. [self-control] During REM sleep, | |
metabolism in the frontal cortex goes way down, disinhibiting the | |
limbic system to come up with the most outlandish ideas. | |
Some extremely difficult studies that make me queasy just to | |
contemplate deprive people or [other] animals of REM sleep | |
preferentially, and the study subjects [fall apart] much faster than | |
they do for the equivalent amount of deprivation of other types of | |
sleep. | |
The marked increase in metabolic activity during REM sleep, and in | |
some of the most inhibited areas of the brain during waking, have | |
suggested to some a sort of "use it or lose it" scenario in which | |
dreaming gives some exercise to otherwise underutilized brain | |
pathways. | |
Both slow wave and REM sleep also seem to play roles in the formation | |
of new memories, the consolidation of information from the previous | |
day, even information that [you might have thought was forgotten]. | |
No one's sure what CIF (corticotropin inhibiting factor) is, or if it | |
really exists, but there's some decent evidence that CIF is a brain | |
chemical that helps bring on slow wave sleep (called "delta | |
sleep-inducing factor"). Thus, sleep deeply, and you turn off | |
glucocorticoid secretion. | |
About an hour before you wake up, levels of CRH, ACTH, and | |
glucocorticoids begin to rise. This is not just because merely | |
rousing from slumber is a mini-stressor, but because those rising | |
stress hormone levels play a role in terminating sleep. | |
# Chapter 12 | |
In many ways, aging can be defined as the progressive loss of the | |
ability to deal with stress... This can be stated more rigorously by | |
saying that many aspects of the bodies and minds of old organisms | |
work fine, just as they do in young ones, so long as they aren't | |
pushed. | |
[If you give young and old people IQ tests] and give them lots of | |
time to complete the test, there is little difference. As you stress | |
the system--in this case, by making the subjects race against a time | |
limit--scores fall... much further among older people. | |
The bizarre thing is that this sequence of events not only occurs in | |
five species of salmon, but also among a dozen species of Australian | |
marsupial mice; cut out their adrenal glands, however, and they too | |
keep living. Pacific salmon and marsupial mice are not close | |
relatives. At least twice in evolutionary history, completely | |
independently, two very different sets of species have come up with | |
the identical trick: if you want to degenerate very fast, secrete a | |
ton of glucocorticoids. | |
The elevated glucocorticoid levels of old age, therefore, arise | |
because of a problem with feedback regulation in the damaged | |
hippocampus. Why are neurons damaged in the hippocampus? It's | |
glucocorticoid exposure... | |
# Chapter 13 | |
We humans also deal better with stressors when we have outlets for | |
frustration... A central feature of an outlet being effective is if | |
it distracts from the stressor. But, obviously, more important is | |
that it also be something positive for you... Another option is to | |
take it out on an innocent bystander. | |
* Social support networks and friends reduce stress. | |
* Predictability makes stressors less stressful. | |
* Control helps. Loss of control and lack of predictive | |
information are closely related. The common theme is that the | |
organism is subjected to novelty. | |
* A perception of things worsening makes it more stressful. | |
# Chapter 14 | |
The defining feature of a major depression is loss of pleasure. | |
Anhedonia [also known as dysphoria] is the inability to feel pleasure. | |
The strikingly different subtypes of depression and their variability | |
suggest not just a single disease, but [multiple] diseases that have | |
different underlying biologies. | |
The pleasure pathway seems to make heavy use of dopamine as a | |
neurotransmitter. The strongest evidence for this is the ability of | |
drugs that mimic dopamine, such as cocaine, to act as euphoriants. | |
ACC: anterior cingulate cortex. And the emotions that the ACC is | |
involved in seem to be negative ones. Induce a positive state in | |
someone and ACC metabolism decreases. In contrast, if you | |
electrically stimulate the ACC in people, they feel a shapeless sense | |
of fear and foreboding. ...its resting level of activity tends to be | |
elevated in people with a depression... Interestingly, the amygdala | |
seems to be hyperactive in depressives as well. | |
Specifically, activation of the left PFC (pre-frontal cortex) is | |
associated with positive moods, and activation of the right PFC, with | |
negative. [This is true in both humans and monkeys.] | |
Glucocorticoid levels are typically abnormal in people who are | |
clinically depressed. | |
[It has been shown that adrenal steroidogenesis inhibitors lessen | |
depression, but these drugs can have some nasty side-effects.] | |
# Chapter 15 | |
Thus among some male baboons, there are at least two routes for | |
winding up with elevated basal glucocorticoid levels, independent of | |
social rank--an inability to keep competition in perspective and | |
social isolation. | |
When it comes to psychological disorders, it seems that increases in | |
the catecholamines have something to do with still trying to cope and | |
the effort that involves, where the overabundance of glucocorticoids | |
seems more a signal of having given up on attempting to cope. | |
[Psychological stress seems to involve the hippocampus.] Instead, | |
anxiety and fear conditioning are the province of a related | |
structure, the amygdala. [The amygdala is about the interpretation | |
of pain.] Remarkably, the amygdala gets sensory information before | |
that information reaches the cortex and causes conscious awareness of | |
the sensation... | |
[Stress and glucocorticoids make the amygdala more excitable.] | |
This final section is about a newly recognized version of an | |
overactive stress-response. And it's puzzling. [These people are | |
objectively pretty functional and well adjusted.] Yet, these people | |
(comprising approximately 5 percent of the population) have | |
chronically activated stress responses. The people in question are | |
said to have "repressive" personalities, and we have all met someone | |
like them. In fact, we usually regard these folks with a tinge of | |
envy--"I wish i had their discipline; everything seems to come so | |
easily to them. How do they do it?" | |
These are the archetypal people who cross all their t's and dot all | |
their i's. They describe themselves as planners who don't like | |
surprises, who live structured, rule-bound lives... Not | |
surprisingly, they don't like ambiguity and strive to set up their | |
world in black and white... They keep a tight lid on their emotions. | |
Stoic, regimented, hardworking, productive, solid folks who never | |
stand out in a crowd... | |
Intertwined with those characteristics is a peculiar lack of | |
emotional expression. | |
Yet even after you cross the anxious self-deceivers off the list, | |
there remains a group of people with tight, constrained personalities | |
who are truly just fine... But they have overactive stress | |
responses. And these... exact a price. | |
Davidson and Andrew Tomarken of Vanderbilt University have used | |
electroencephalographic (EEG) techniques to show unusually enhanced | |
activity in a portion of the frontal cortex of repressors... it takes | |
a lot of [mental] work... | |
# Chapter 16 | |
Pleasure is the anticipation of a reward; from the standpoint of | |
dopamine, the reward is almost an afterthought. [Dopamine fuels the | |
behavior.] ...the strength of these pathways can change, just like | |
any other part of the brain. This is how gratification postponement | |
works--the core of goal-directed behavior is expectation. Soon we're | |
foregoing immediate pleasure in order to get good grades in order to | |
get into a good college in order to get a good job in order to get | |
into the nursing home of our choice. | |
[When there is simply a high probability of reward rather than | |
certainty] there is even greater release of dopamine. [intermittent | |
reinforcement] | |
As we saw, experience moderate and transient stress, and memory, | |
synaptic plasticity, and immunity are enhanced. Same thing here | |
[with maximized dopamine release. Moderate but not excessive stress | |
makes things more pleasurable.] We have a name for such transient | |
stress. We call it "stimulation." | |
If you flood a synapse with a gazillion times more of a | |
neurotransmitter than is usually the case, the recipient neuron has | |
to compensate by becoming less sensitive. This is the addiction | |
cycle of escalating drug use. | |
Early on, addiction is about "wanting" the drug, anticipating its | |
effects, and about how high those dopamine levels are when they're | |
pouring out in a drug-induced state. With time there's the | |
transition to "needing" the drug, which is about how low the dopamine | |
lows are without the addiction. The stranglehold of addiction is | |
when it is no longer the issue of how good the drug feels, but how | |
bad its absence feels. | |
# Chapter 17 | |
> Medicine is a social science, and politics nothing but medicine | |
> on a large scale. Physicians are the natural attorneys of the | |
> poor. --Rudolph Virchow | |
The purpose of this chapter is to show how your place in society, and | |
the sort of society it is, can leave an imprint on patterns of | |
disease while you are alive, and to show that part of understanding | |
this imprint incorporates the notion of stress. | |
As a final variable, it is not just rank that is an important | |
predictor of the stress-response, not just the society in which the | |
rank occurs, or how a member of the society experiences both; it's | |
also personality... | |
If you want to see an example of chronic stress, study poverty. ... | |
All these hardships suggest that low socioeconomic status | |
(SES--typically measured by a combination of income, occupation, | |
housing conditions, and education) should be associated with chronic | |
activation of the stress-response. Only a few studies have looked at | |
this, but they support this view. | |
...if you have a bunch of people of the same gender, age, and | |
ethnicity and you want to make some predictions about who is going to | |
live how long, the single most useful fact to know is each person's | |
SES. If you want to increase the odds of living a long and healthy | |
life, don't be poor. | |
Findings such as these go back centuries. ...the diseases that people | |
were dying of most frequently a century ago are dramatically | |
different from the most common ones now. Different causes of death, | |
but same SES gradient, same relationship between SES and health. | |
Which tells you that the gradient arises less from disease than from | |
social class. Thus the "roots [of the SES health gradient] lie | |
beyond the reach of medical therapy." | |
[Being poor sets you up for poor health more than poor health sets | |
you up for being poor.] | |
In the United States, poor people (with or without health insurance) | |
don't have the same access to medical care as do the wealthy. As one | |
example of this, a 1967 study showed that the poorer you are judged | |
to be (based on the neighborhood you live in, your home, your | |
appearance), the less likely paramedics are to try to revive you on | |
the way to the hospital. In more recent studies, SES influenced your | |
likelihood of receiving physical, occupational, or speech therapy, | |
and how long you waited until undergoing surgery to repair the | |
damaged blood vessel that cause the stroke. | |
In a place like England, the SES gradient has gotten worse over this | |
century, despite the imposition of universal health care allowing | |
everyone equal health care access. It's not only the case that only | |
poor people are less healthy than everyone else. Instead, for every | |
step lower in the SES ladder, there is worse health, and the lower | |
you get in the SES hierarchy, the bigger is each step of worsening | |
health. ...the gradient [also] exists for diseases that have nothing | |
to do with access [to health care. Perhaps this is related to the | |
complete lack of preventative medicine.] | |
Poorer people in westernized societies are more likely to drink and | |
smoke excessively. These excesses take us back to the last chapter | |
and having trouble "just saying no" when there are few yes's. [crap | |
life syndrome] Moreover, the poor are more likely to have an | |
unhealthy diet--in the developing world, being poor means having | |
trouble affording food, while in the western world, it means having | |
trouble affording HEALTHY food. Thanks to industrialism, fewer jobs | |
in our society involve physical exertion and, when combined with the | |
costs of membership in some tony health club, the poor get less | |
exercise. They are more likely to live near a toxic dump, be mugged, | |
have inadequate heat in the winter, live in crowded conditions | |
(thereby increased exposure to infectious diseases). The list seems | |
endless, and they all adversely impact health. | |
Being poor is statistically likely to come with another risk | |
factor--being poorly educated. Statistically, being better educated | |
predicts that your community of friends and relatives is better | |
educated as well, with those attendant advantages. | |
[However] For the same risk factors and the same lack of protective | |
factors, throw in poverty and you're more likely to get sick. So | |
differential exposure to risk factors or protective factors does not | |
explain a whole lot. | |
...the SES gradient is not really about a distribution that bottoms | |
out at being poor. It's not about being poor. It's about feeling | |
poor, which is to say, it's about feeling poorer than others around | |
you. ...what someone thinks and feels their SES is their "subjective | |
SES." [Subjective SES] is at least as good a predictor of these | |
health measures as is one's actual SES, and, in some cases, it is | |
even better. | |
Adler shows that subjective SES is built around education, income, | |
and occupational position, plus satisfaction with standard of living, | |
and feeling of financial security about the future. | |
But thanks to urbanization, mobility, and the media that makes for a | |
global village, something absolutely unprecedented can now occur--we | |
can now be made to feel poor, or poorly about ourselves, by people we | |
don't even know. | |
...in societies that have more income equality, both the poor and the | |
wealthy are healthier than their counterparts in a less equal society | |
with the same average income. | |
What Kawachi shows is that the more income inequality in a society, | |
the lower the social capital, and the lower the social capital, the | |
worse the health. Findings such as these make perfect sense to | |
Wilkinson. In his writings, he emphasized that trust requires | |
reciprocity, and reciprocity requires equality. In contrast, | |
hierarchy is about domination, not symmetry and equality. By | |
definition, you can't have a society with both dramatic income | |
inequality and lots of social capital. | |
So income inequality, minimal trust, [and] lack of social cohesion | |
all go together. | |
How does lots of social capital turn into better health throughout a | |
community? Less social isolation. More rapid diffusion of health | |
information. Potentially, social constraints on publicly unhealthy | |
behaviors. Less psychological stress. Better organized groups | |
demanding better public services (and, related to that, another great | |
measure of social capital is how many people in a community bother to | |
vote). | |
...the more economically unequal a society, the more crime. | |
Critically, income inequality is consistently a better predictor of | |
crime than poverty per se. ...poverty amid plenty predicts more | |
crime--but not against the wealthy. The have-nots turn upon the | |
have-nots. | |
If you want to improve health and quality of life, and decrease the | |
stress, for the average person in a society, you do so by spending | |
money on public goods--public transit, safe streets, clean water, | |
public schools, universal health care. The bigger the income | |
inequality is in a society, the greater the financial distance | |
between the wealthy and the average. The bigger [this distance], the | |
less benefit the wealthy will feel from expenditures on the public | |
good. This secession of the wealthy pushes toward private affluence | |
and public squalor. And more public squalor means more of the daily | |
stressors and allostatic load that drives down health for everyone. | |
Agriculture is a fairly recent human invention, and in many ways it | |
was one of the great stupid moves of all time. Hunter-gatherers have | |
thousands of wild sources of food to subsist on. Agriculture changed | |
all that, generating an overwhelming reliance on a few dozen | |
domesticated food sources, making you extremely vulnerable to the | |
next famine, the next locust infestation, the next potato blight. | |
Agriculture allowed for the stockpiling of surplus resources and | |
thus, inevitably, the unequal stockpiling of them--stratification of | |
society and the invention of classes. Thus, it allowed for the | |
invention of poverty. | |
# Chapter 18 | |
...amid a population of, say, 50 subjects there have to be 6 subjects | |
where Something Or Other is improving with age. Their kidney | |
filtration rates have gotten BETTER, their blood pressures have | |
DECREASED, they do BETTER on memory tests. This pattern used to be a | |
statistical irritant to gerontologists. | |
If a rat is handled [physical touch] during the first few weeks of | |
its life, it secretes less glucocorticoids as an adult. | |
Among this population [in George Vaillant's research], which subset | |
has had the greatest health, contentment, and longevity in old age? A | |
subset with an array of traits, apparently before the age of 50: no | |
smoking, minimal alcohol use, lots of exercise, normal body weight, | |
absence of depression, a warm, stable marriage, and a mature, | |
resilient coping style (which seems built around extroversion, social | |
connectedness, and low neuroticism). Findings like these have | |
emerged from other studies. | |
Another literature shows the tremendous gerontological benefits of | |
being respected and needed in old age. [This reminds me of Malidoma | |
Some's writing about tribal elders and children taking care of each | |
other.] | |
We can change the way we cope, both physiologically and | |
psychologically. Examples: exercise and psychotherapy. | |
Sheer repetition of certain activities can change the connection | |
between your behavior and activation of your stress response. | |
[Studies show that when you allow patients to self-medicate, the | |
total amount of painkillers consumed decreases. Control and | |
predictability help to manage the pain.] | |
In one study, residents of a nursing home were given more | |
responsibility for everyday decision making. They were made | |
responsible for choosing their meals for the next day, signing up in | |
advance for social activities, picking out and caring for a plant in | |
their room... People became more active--initiating more social | |
interactions--and describing themselves in questionnaires as happier. | |
Their health improved, as rated by doctors unaware of whether they | |
were in the increase-responsibility group or the control group. Most | |
remarkable of all, the death rate in the former group was half that | |
of the latter. | |
[Even just a moderate increase in control produces great results.] | |
When the staff present encouraged them, performance improved; when | |
the staff present [merely] helped them, performance decline. | |
These studies generated some simple answers to coping with stress | |
that are far from simple to implement in everyday life. They | |
emphasize the importance of manipulating feelings of control, | |
predictability, outlets for frustration, social connectedness, and | |
the perception of whether things are worsening or improving. "More | |
control, more predictability, more outlets, more social support" is | |
not some sort of mantra to be handed out indiscriminately, along with | |
a smile button. | |
* Exercise enhances mood and blunts the stress response only for a | |
few hours to a day after the exercise session. | |
* Exercise is stress reducing as long as it is something you | |
actually want to do... | |
* The studies are quite clear that aerobic exercise is better for | |
your health. | |
* Exercise needs to occur on a regular basis and for a sustained | |
period. | |
* Too much can be as bad as too little. | |
When done on a regular, sustained basis (that is to say, something | |
close to daily, for 15 to 30 minutes at a time), meditation seems to | |
be pretty good for your health, decreasing glucocorticoid levels, | |
sympathetic tone, ... | |
An overabundance of information can be stressful as well. | |
Having an illusory sense of control in a bad setting can be so | |
pathological that one version of it gets a special name in the health | |
psychology literature. As Sherman James defines it, John Henryism | |
involves the belief that any and all demands can be vanquished, so | |
long as you work hard enough. This is the epitome of individuals | |
with an internal locus of control--they believe that, with enough | |
effort and determination, they can regulate all outcomes. | |
What's so wrong with that? Nothing, if you have the good fortune to | |
live in the privileged, meritocratic world in which one's efforts | |
truly do have something to do with the reward one gets, and in a | |
comfortable, middle-class world, an internal locus of control does | |
wonders. However, in a world of people born into poverty, John | |
Henryism is associated with a market risk of hypertension and | |
cardiovascular disease. | |
Often, one of the strongest stress-reducing qualities of social | |
support is the act of GIVING social support, to be needed. | |
What's religiosity versus spirituality? The former is about an | |
institutionalized system with a historical precedent and a lot of | |
adherents; the latter is more personal. When comparing religious | |
people with people who define themselves as spiritual but without a | |
religious affiliation, the former tend to be older, less educated, | |
and lower in socioeconomic status, with a higher percentage of men. | |
So religiosity and spirituality can be very different things. But | |
despite that, the health literature says roughly similar things about | |
both... | |
So religiosity is a tough subject to do real science on, something | |
the best people readily point out. Another thing that folks like | |
Sloan and Thoresen agree upon is that when you do see a legitimate | |
link between religiosity and good health, you don't know which came | |
first. [correlation versus causation] | |
And once you've [controlled for lifestyle factors such as drinking | |
and smoking], Thoresen and Sloan are still mostly in agreement, which | |
is that religiosity does predict health to some extend in a few areas | |
of medicine. | |
Moreover, deeply religious people (by their own assessment) derive no | |
more of what health benefits there are than the less deeply | |
religious. [The effects] are more about healthy people staying | |
healthy than sick people staying alive and recovering faster. | |
In the face of some stressor, "coping" can take a variety of forms. | |
Implicit in switching to the optimal strategy for the particular | |
circumstance is having the cognitive flexibility to switch | |
strategies. Coping responses built around fixed rules and flexible | |
strategies. | |
I would apple the 80/20 rule to stress management: 80 percent of the | |
stress reduction is accomplished with the first 20 percent of effort. | |
But once you sincerely want to change, the mere act of making an | |
effort can do wonders. | |
author: Sapolsky, Robert M. | |
detail: gopher://gopherpedia.com/0/Why_Zebras_Don't_Get_Ulcers | |
LOC: QP82.2.S8 S266 | |
tags: book,health,non-fiction,science | |
title: Why Zebras Don't Get Ulcers | |
# Tags | |
book | |
health | |
non-fiction | |
science |