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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, worrying about mortgages, relationships, and promotions.
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.
A stressor can also be the anticipation of that happening.
Homeostasis is about tinkering with this valve or that gizmo. Allostasis is about the brain coordinating body-wide changes, often including changes in behavior.
One of the hallmarks of the stress-response is the rapid mobilization of energy from storage sites and the inhibition of further storage.
During stress, growth and tissue repair is curtailed, sexual drive decreases in both sexes; females are less likely to ovulate or to carry pregnancies to term, while males begin to have trouble with erections and secrete less testosterone.
With sufficiently sustained stress, our perception of pain can become blunted.
It is not so much that the stress-response runs out, but rather, with sufficient activation, that the stress-response can become more damaging than the stressor itself, especially when the stress is purely psychological.
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.
Sympathetic arousal is a relative marker of anxiety and vigilance, while heavy secretion of glucocorticoids is more a marker of depression.
High levels of cholesterol, particularly of “bad” cholesterol, certainly increase the risk for cardiovascular disease. But they’re not a great predictor; a surprising number of folks can tolerate high levels of bad cholesterol without cardiovascular consequences, and only about half of heart attack victims have elevated cholesterol levels.
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.
Whenever you inhale, you turn on the sympathetic nervous system slightly, minutely speeding up your heart. And when you exhale, the parasympathetic half turns on, activating your vagus nerve in order to slow things down (this is why many forms of meditation are built around extended exhalations).
Mysterious cases still occur, however, of seemingly healthy thirty-year-olds, victims of sudden cardiac death, who show little evidence of atherosclerosis on autopsy.
Fibrillation seems to be the critical event in sudden cardiac death, as judged by animal studies (in which, for example, ten hours of stress for a rat makes its heart more vulnerable to fibrillation for days afterward).
Fat cells then release some newly discovered hormones that get other tissues, like muscle and liver, to stop responding to insulin as well. Stress promotes insulin resistance.
As of 1990, about 15 percent of Americans over age sixty-five had adult-onset diabetes. That was considered a health disaster then. As of a decade later, there’s been a 33 percent increase above that, and among middle-aged adults as well.
Adult-onset diabetes has even become more prevalent among kids than juvenile diabetes, which is pretty horrifying.
The official numbers are that stress makes about two-thirds of people hyperphagic (eating more) and the rest hypophagic.
Thus, we appear to have a problem here. CRH inhibits appetite, glucocorticoids do the opposite.
Much of preventative medicine is a demonstration that vast numbers of adverse health situations can be reversed—in fact, that is a premise of this book.
“Man cannot live by milk alone. Love is an emotion that does not need to be bottle- or spoon-fed,” wrote Harlow.
Not everything in the body has to have an explanation in terms of evolutionary adaptiveness.
Thus, early on during exposure to a stressor, glucocorticoids and other stress-responsive hormones transiently activate the immune system, enhancing immune defenses, sharpening them, redistributing immune cells to the scenes of infectious battle. Because of the dangers of the systems overshooting into autoimmunity, more prolonged glucocorticoid exposure begins to reverse these effects, bringing the system back to baseline.
So collectively, we have, with the exception of two studies concerning one type of cancer, no overall suggestion that stress increases the risk of cancer in humans.
What if your cancer has been cured? Does stress increase the risk of it coming back? The handful of studies on this subject don’t suggest that there’s a connection—a few say yes, an equal number, no.
Opioids turn out to be the exception to the rule. Stress-induced analgesia does not go on forever, and the best evidence ascribes this to depletion of opioids. You are not permanently out of business, but it takes a while for supply to catch up with demand.
Understand what goes wrong next in a “Cushingoid” patient and you understand half of this book—high blood pressure, diabetes, immune suppression, reproductive problems, the works.
So should you avoid taking glucocorticoids for your autoimmune disease in order to avoid the possibility of accelerated hippocampal aging somewhere down the line? Almost certainly not—these are often devastating diseases and glucocorticoids are often highly effective treatments. Potentially, the memory problems are a particularly grim and unavoidable side effect.
Consider how bizarre and maladaptive this is. Lion chases you; you secrete glucocorticoids in order to divert energy to your thigh muscles—great move. Go on a blind date, secrete glucocorticoids in order to divert energy to your thigh muscles—probably irrelevant. Have a grand mal seizure, secrete glucocorticoids in order to divert energy to your thigh muscles—and make the brain damage worse. This is as stark a demonstration as you can ask for that a stress-response is not always what you want your body to be having.
Gerontologists studying the aging process find increasing evidence that most of us will age with a fair degree of success. There’s far less institutionalization and disability than one might have guessed. While the size of social networks shrink with age, the quality of the relationships improves.
The control element is more powerful than the demand one—low demand and low control is more damaging to one’s health than high demand and high control.
