The whole time I've been traveling lately, disliking a lot of it, feeling frayed at the edges by it, I've been carrying around and trying to read a book, The Hour Between Dog and Wolf, by John Coates. Great book, by the way..
The second-last chapter is, Toughness: Can we control our stress response? Here is a synopsis.
1. Repeated stresses that do not have physical expression involved, but have lots of cortisol, harm the body -> hypertension, type II diabetes, heart disease, immune disorders, depression:
"..like the fire brigade, the stress response may save our house from an emergency only to destroy it with water damage."2. Can cortisol be turned off? Hard to do. E.g., open field experiment with rodents. Putting a rodent in an open field produces a predictable stress response (freezing, immobility, defecation, elevated stress hormone). Repeated exposure habituates the animal - it's behaviour normalizes, however, the stress hormone levels remain high. Its adrenal glands still respond to "danger" even though the animal acts less stressed or afraid. Likewise, human physiology and behaviour can show similar discrepancy.
3. Stress is largely a physiological preparation for physical action. Physiology can be "trained". Greater mental and physical stamina can be attained. We can "toughen" against fatigue, anxiety, and psychiatric disorder associated with stress response.
4. Physical toughness might include things like strength, posture, coordination, and endurance. Mental toughness might include a particular attitude to novel events, seeing them as a challenge, opportunity for gain. An untoughened individual might see novel events as dreadful, potentially harmful. Each attitude has distinct physiology. What does resilience consist of? One must consider catabolic hormones, anabolic hormones, amines, and the vagus nerve.
5. Catabolic hormones (e.g., cortisol) break down energy stores (e.g., muscle) for immediate use. "By breaking down muscles and converting them into immediately useable forms of energy, cortisol in effect stripmines our body for nutrients.. our body begins to disintegrate under its caustic influence." Cortisol has to be turned off ASAP, after a couple days, or at most, a couple weeks, or the damage is hard to reverse. It provides us with metabolic support in a crisis but it's a big price to pay, long term, so its production and release should occur only sporadically and be followed by a recovery period.
6. Anabolic hormones include testosterone and growth hormone. They rebuild the body, convert amino acids to muscle, calcium to bone, insulin removes glucose from blood and puts it in the liver, insulin-like growth factor (IGF) rejuvenates body and brain cells. Healthy people have a high ratio of anabolic hormones to catabolic ones; this is called the growth index. A high growth index = "thriving". It depends on rest, not growing old (which involves decline in testosterone and growth hormone). It can be linked to blood pressure, body-mass index, hip to waist ratio, cholesterol levels, blood glucose levels, noradrenaline and cortisol levels measured from urine. This is a reliable predictor of future health.
7. Amines are substances produced by cells in the brain. Included are dopamine, noradrenaline and adrenaline, several others including serotonin. They reach targets rapidly, focus our attention, release glucose and promote fight/flight response same as does cortisol, but they switch off faster than cortisol. "..a toughened individual is one who enjoys a powerful and immediate amine reaction when challenged, so he or she does not need to draw on the longer-acting and more potent cortisol response." In such a person, amine levels are lower at rest. They turn on quickly with stress and turn off fast. Stress is handled without emotional distress. "The research into toughness has suggested that our brain silently compares the demands being made on us against the resources we can draw on (taking into account our training and skill). If our resources are sufficient we view the event as a challenge and relish it; if not, we see it as a threat and shrink from it." Amine producing cells can be overworked though. They need rest to replenish themselves. Depletion of dopamine leads to lack of motivation, depression, anhedonia. Depletion of noradrenaline cells leads to lack of arousal and enthusiasm, and to learned helplessness.
Amine cells can be trained to increase their production! "..toughened people endure a sustained challenge without depleting the amines in their brain or succumbing to learned helplessness. [they have] all the cognitive and metabolic effects of the amines while suppressing the damage done by chronic exposure to cortisol. Such a profile is found, for example, in elite athletes."
8. The vagus nerve calms everything down, conserves energy, and together with anabolic hormones helps repair. Good vagal "tone" found in toughened individuals acts as a brake; efficient cardiac output is coupled with low blood pressure in peripheral arteries. Good tone is associated with good heart rate variability. Those with poor vagal "tone" tend to over react to mild stressors, with a much shorter distance to go before fight/flight responses engage. Their heart rate variability is low. High heart rate variability is associated with high ratio of anabolic to catabolic hormones.
9. The biggest assist we have to become toughened, more resilient physiologically, build up our amines, is exercise. "Exercise expands the productive capacity of our amine-producing cells, helping to inoculate us against anxiety, stress, depression, and learned helplessness. It also floods our brains with what are called growth factors, and these keep existing neurons young and new neurons growing - some scientists call these growth factors "brain fertilizer" - so our brains are strengthened against stress and aging. A well-designed regime of physical exercise can be a boot camp for the brain." Also helpful: exposure to cold weather, cold water, thermal demand. Thermoregulation was an advance of mammals, then humans who evolved hairless bodies that can sweat. Thermoregulation may be coupled somehow with emotional arousal. (E.g., blushing, hot flashes.. ) Developing cold tolerance, or tolerance to thermal stress, may also increase emotional stability. Eliminating thermal stress might atrophy a large, fundamental part of our physiology.
10. Becoming more interoceptively aware (mindfulness training) will help us recognize fatigue sooner, and change activities, to protect amines. "Fatigue should be understood as a signal our body and brain use to inform us that the expected return from our current activity has dropped below its metabolic cost. The brain quietly searches for the optimal allocation of attentional and metabolic resources, and fatigue is one way it communicates its results.. the cure for fatigue... is not a rest, it is a fresh task." Also, having locus of control over one's activity (e.g., in the workplace) reduces fatigue. Novelty is rejuvenating. At other times the brain favours familiarity and more vagus nerve action.
Bottom line: learn to exercise regularly. Make exercise your friend. Stave off your brain's dismayed perception of its own entropy.
SELECTED REFERENCES USED BY THE AUTHOR
1. Sapolsky R; Why Zebras Don't Get Ulcers. Holt Paperbacks; Third Edition edition (Aug 26 2004) [link is to an online pdf] Also, 3 min video on your tube.
2. Chrousos G; Stress and disorders of the stress system. Nat Rev Endocrinol. 2009 Jul;5(7):374-81.
3. LeDoux J; The Emotional Brain: The Mysterious Underpinnings of Emotional Life. New York Touchstone 1996
4. Amini T, Lannon F, Lewis R; A General Theory of Love. New York Vintage 2001
5. Hennessey J, Levine S; Stress, arousal, and the pituitary-adrenal system: a psychoendocrine hypothesis. Progress in psychobiology …, 1979 - New York: Academic Press
6. Jim Blascovich, Joe Tomaka; The BiopsychosocialModel of ArousalRegulation. Advances in Experimental Social Psychology Volume 28, 1996, Pages 1–51
7. Blascovich J, Mendes WB; Challenge and Threat Appraisals: The Role of Affective Cues. Ch 3 in Feeling and Thinking: The Role of Affect in Social Cognition, edited by Forgas JP, Cambridge University Press; 1 edition (Jun 4 2001)
ADDITIONAL REFERENCES I FOUND
1. Rod K. Dishman, Hans-Rudolf Berthoud, Frank W. Booth, Carl W. Cotman, V. Reggie Edgerton, Monika R. Fleshner, Simon C. Gandevia, Fernando Gomez-Pinilla, Benjamin N. Greenwood, Charles H. Hillman, Arthur F. Kramer, Barry E. Levin, Timothy H. Moran, Amelia A. Russo-Neustadt, John D. Salamone, Jacqueline D. van Hoomissen, Charles E. Wade, David A. York, Michael J. Zigmond; Neurobiology of Exercise. Obesity Volume 14, Issue 3, pages 345–356, March 2006 (Full access)
2. David R. Vago and David A. Silbersweig; Self-awareness, self-regulation, and self-transcendence (S-ART): a framework for understanding the neurobiological mechanisms of mindfulness. Front. Hum. Neurosci. 6:296. 25 October 2012 (Full access)