Stress and Its Effects
on the Body, Brain & Mind
How We Become Addicted to Stress
And How It Makes Us Old & Cynical
Stress can be a killer. Stress can make us miserable ... and miserable to be around. But stress can also wake us up, makes us pay attention, makes life lively. Without stress strength suffers; bones start shedding calcium if we don’t put regular loads on them. Some seem to crave stress, going out of their way to put themselves in dangerous yet thrilling situations.
How could this be? Why would the same stressful situations that would send some of us packing draw others in like moths to the flame? What makes some of us run away from gunfire ... and others towards it?
How the Stress Response Works
One of the oldest parts of the brain is the hypothalamus. It lives deep in the brain, just in front of the top of the spine. The hypothalamus registers emotion.
The hypothalamus also controls many unconscious body functions. Temperature control, sweat, heart rate: all under hypothalamic control. In this role the hypothalamus also orchestrates the stress response.
The hypothalamus is part of the HPA axis, the Hypothalamus-Pituitary-
Adrenal axis. These endocrine glands work together to switch our body's nervous system back and forth between two operating modes: parasympathetic and sympathetic. The pituitary sits front of the hypothalamus; the adrenals are just above the kidneys, protected by the lowest ribs.
When the parasympathetic dominates our heart rate slows, muscular tension eases, we digest our food and get to sleep easily. When the parasympathetic is in charge our bodies go into a special metabolic phase called anabolic. In anabolic mode our metabolisms gear up to rebuild our reserves and repair worn out, tired cells and tissues.
Human bodies work constantly to identify worn out cells and tissues, break them down and replace them with fresh cells. When we're healthy we get new skin every seven weeks or so; new bones about every ten years. In between these two extremes every part of the body is regularly red-tagged, broken down, rebuilt. This process, called tissue replacement is one of the things that distinguishes the living from the dead. It's driven by protein turnover ... essentially, how quickly our bodies can generate new protein to replace the proteins used up as the body does its work.
As we get older protein turnover ... and therefore tissue replacement ... slows down. We call it aging. So it’s important to recognize that parasympathetic, relaxed states slow aging by making it possible for the body to go into anabolic, rebuild-and-repair mode ... typically while we sleep.
Sympathetic mode is the exact opposite. It's stress mode. When the hypothalamus perceives a threat it triggers an endocrine cascade that signals the adrenals to release adrenaline. This wakes us up and fills us with energy. Hearts beat faster, our cerebral cortex (where consciousness lives, right behind the forehead) snaps to attention. Hyperalert and energetic, we're ready to meet any threat. Or maybe we’re just speeding.
At the same time another brain structure called the locus ceruleus tells sympathetic nerve endings throughout the body to secrete norepinephrine (NE). NE binds to special receptors on cells throughout the body, exciting them.1 When a trucker's air-horn goes off suddenly as we walk down the street and we jump, it's NE jerking our strings.
Why We Become Addicted to Stress
The body keeps a certain amount of quick energy in reserve, in glycogen deposits within each cell. When adrenaline and NE flood the bloodstream they tell glycogen to break down quickly into blood sugar; this flood of sugar immediately increases the energy available to our muscles, organs and brains.
It also produces a dopamine surge. Dopamine is the “reward” neurotransmitter, the one that tells us we like something. Dopamine is the neurotransmitter of falling in love; it’s the one cocaine uses to addict us.
Dopamine rewires the brain to repeat whatever behaviors created the dopamine surge in the first place. And that’s why some of us can become addicted to drama: drama creates stress, stress causes the release of adrenaline and NE, blood sugar levels rise and give us a dopamine payoff. Voila! Addiction to drama.
The Cost of Stress Addiction ... Rapid Aging
But here’s the problem: if the stressor is sustained more than a few moments glucocorticoids (GCs) are released. Adrenaline and NE are released quickly and clear quickly; GCs stick around for awhile. GCs start the process of rebuilding glycogen stores, lowering blood sugar levels. They send amino acids, the building blocks of protein, to the liver where they're broken down into free fatty acids and released into the bloodstream.2,3 This metabolic phase is called catabolism. In catabolic phase our bodies literally digest themselves.
All of these steps are designed to fuel our bodies' ability to run or fight for our lives (adrenaline and NE,) then recover from the immediate threat while we maintain the hypervigilance (glucocorticoids) we need to have an early warning if the danger returns.
If you've ever been in an auto accident that you saw coming, the moment just before impact when everything slows down is the effect of adrenaline and NE. If we get in the car the next day and become anxious, that's glucocorticoids at work.
In the normal course of things our bodies are in either anabolic or catabolic mode; we can't be in both simultaneously. Think of the sympathetic nervous system as the gas pedal and parasympathetic as the brake. If we stand on the gas and the brake at the same time things don't work so well. So the endocrine system is designed to prevent it.
This is really just common sense: the more stressed we are the harder it is to relax. So if we want to give our bodies a chance to heal and refresh themselves we have to find a way to get back to a relaxed, parasympathetic state.
Our problem today is that the nature of our stressors have changed over the last few thousand years. Today we're stressed more by social situations than we are by real flesh-and-blood predators so we rarely actually bother to run or fight ... but our bodies are still primed for just that response.
Glucocorticoids can be particularly problematic. GCs slow protein production.4,5 And that means they the rate of tissue replacement so we age faster. They increase the responsiveness of arterial muscle to sympathetic stimulation,6 helping shunt blood away from the gut. This makes it harder for us to absorb nourishment from our food and can set the stage for chronic inflammation resulting from immune reactions to incomplete protein digestion.7,8 A steadily increasing body of evidence implicates these inappropriate immune reactions as a cause of some emotional disturbances.9,10,11,12
Chronic Stress + Time = Cynicism.
We Become Difficult People.
As if that wasn’t enough, GCs also age the hippocampus, the very part of the brain involved in memory and therefore in helping the hypothalamus register a threat. The hippocampus and the stress-response orchestrating hypothalamus both have usually dense populations of glucocorticoid (GC) receptor sites because it's their job to recognize when enough GCs are in circulation and stop their production.13 Essentially the hippocampus serves as the "thermostat” for the stress response - thus the unusually dense population of GC receptor sites. We want that part of the brain to be more sensitive to GCs.
The problem is, since GCs shift us from anabolic to catabolic mode, chronic oversecretion of GCs over time can weaken the neurons in this key brain region.14 That makes them much more subject to damage and even death when subjected to the kinds of routine insults (hunger, intoxication, overstimulation) to which neurons are exposed in the normal course of their lives.15,16
The bottom line: people who live unusually stressed lives can have a hard time turning off their stress hormones. A chronically overactive stress response tells the brain's emotional center that we're constantly under threat. This can leave us in a depressed, hostile, withdrawn, chronically cynical or negative mood. It can also impair thinking, our ability to focus, concentrate, learn and reason.
Evidence suggests that how much a particular human experiences these effects17 appears to fluctuate along with the magnitude, frequency and duration of the metabolic and social stresses a person was exposed to as a child.18
So if we want to be healthy and live effectively and productively it's vital to find ways of easing our stress. And that’s why we’re here ... to help you identify those strategies and put them to work.
1. Tsigos, C., Chrousos, G.P. 2002. Hypothalamic-pituitary-adrenal axis, neuroendocrine factors and stress. Journal of Psychosomatic Research. 53(4):865-871.
2. Vander, A., et al. 2003. Human Physiology, Ninth Edition. New York: McGraw-Hill.
3. Mizock, B.A. 1995. Alterations in carbohydrate metabolism during stress: a review of the literature. American Journal of Medicine. 98(1):75-84.
4. Sheffield-Moore, M., Urban, R.J. 2004. An overview of the endocrinology of skeletal muscle. Trends in Endocrinology and Metabolism. 15(3):110-115.
5. Umpleby, A.M., Russel-Jones, D.L. 1996. The hormonal control of protein metabolism. Bailliere's Clinical Endocrinology and Metabolism. 10(4):551-570.
6. Whitworth, J.A., et al. 1996. Mechanisms of cortisol-induced hypertension in humans. Steroids. 60(1):76-80.
7. Bhatia, V., Tandon, R.K. 2005. Stress and the gastrointestinal tract. Journal of Gastrology and Hepatology. 20(3):332-339.
8. Monnikes, H., et al. 2001. Role of stress in functional gastrointestinal disorders. Evidence for stress-induced alterations in gastrointestinal motility and sensitivity. Digestive Diseases. 19(3):201-211.
9. Logan, A.C., Katzman, M. 2005. Major depressive disorder: probiotics may be an adjuvant therapy. Medical Hypotheses. 63(3):533-538.
10. Elenkov, I.J., et al. 2005. Cytokine dysregulation, inflammation and well-being. Neuroimmunomodulation. 12(5):255-269.
11. Schiepers, O.J., et al. 2005. Cytokines and major depression. Progress in Neuropsychopharmacology and Biological Psychiatry. 29(2):201-217.
12. Anisman, H., Merali, Z. 2003. Cytokines, stress and depressive illness: brain-immune interactions. Annals of Medicine. 35(1):2-11.
13. Sapolsky, R., Zola-Morgan, S., Squire, L. 1991. Inhibition of glucocorticoid secretion by the hippocampal formation in the primate. The Journal of Neuroscience. 11:3695
14. Sapolsky, R.M. 1992. Stress, the Aging Brain, and the Mechanisms of Neuron Death. Cambridge: The MIT Press. 310-314.
15. Uno, H. et al. 1994. Neurotoxicity of glucocorticoids in the primate brain. Hormones and Behavior. 28(4):336-348.
16. Sapolsky, R.M., et al. 1990. Hippocampal damage associated with prolonged glucocorticoid exposure in primates. The Journal of Neuroscience. 10(9):2897-2902.
17. These are only some of the effects unconscious diet habits may have; there are plenty of others.
18. Meyer, S.E., Chrousos, G.P., Gold, P.W. 2001. Major depression and the stress system: a life span perspective. Developmental Psychopathology. 13(3):565-580.