Stress activates adaptive responses. The body marshals its forces to confront a threat and, generally, does a good job of protecting us in the short run. So why can stress also be so bad for our bodies and brains?
Stress can prematurely age us and leave us chronically fatigued or depressed. When exposure to stress — whether from a traumatic event to just the daily hassle of rush hour traffic or too much email — disrupts the body's internal balance ("homeostasis"), it can go one of three general ways: the body can regain its normal equilibrium once the stress has passed or it can become stuck in an over- or under-aroused state. How a person copes with stress — by reaching for a beer or cigarette as opposed to heading to the gym — also plays a big role in the impact stress will have on our bodies.
How a person copes with stress — by reaching for a beer or cigarette as opposed to heading to the gym — also plays a big role in the impact stress will have on our bodies.
Another aspect of cortisol action is called "containment." Many physiological systems are pitted against one another so that neither system can get out of control. The initial, first line response to many noxious or pathogenic agents is normally "contained" by circulating levels of cortisol. This is why we take corticoids for an inflammation or skin irritation. Cortisol also contains acquired immune responses, and this is particularly useful when those responses are harmful, such as in an allergy or an autoimmune disorder.
All of these adaptive responses are described by the term "allostasis" which means "maintaining stability, or homeostasis, through change."1 The body actively copes with a challenge by expending energy and attempting to put things right. Most of the time it succeeds but the real problems arise when the systems involved in allostasis don't shut off when not needed or don't become active when they are needed.
For our metabolism, the overactivity of the ANS and increased cortisol secretion produce elevated levels of sugar in the blood ("hyperglycemia"). As little as a week of inadequate sleep, say 75% of normal, can raise evening levels of blood sugar. If prolonged, what can result is a rise of insulin, the hormone manufactured by the pancreas to control sugar metabolism. If this situation goes on for a long time, continued hyperactivity of the ANS and elevated cortisol will lead the body down the path to type 2 diabetes. Elevated levels of cortisol, as in depressive illness, are also linked to gradual demineralization of bone.
Increased cortisol secretion produces elevated levels of sugar in the blood ("hyperglycemia"). As little as a week of inadequate sleep can also raise evening levels of blood sugar. [Eventually,] hyperactivity of the ANS and elevated cortisol will lead the body down the path to type 2 diabetes
For the cardiovascular system, the elevation of ANS activity, combined with hyperglycemia and too much insulin ("hyperinsulinemia") promote both hypertension and harmful metabolic conditions, as blood cholesterol rises and HDL, the so-called good cholesterol drops. This one-two punch accelerates hardening of the arteries ("arteriosclerosis"). Blood pressure surges seem particularly important. Among monkeys living in social hierarchies, the dominant males show accelerated atherosclerosis when the hierarchy is unstable and they have to continuously fight for their position. Treating these animals with beta blockers, pharmaceuticals used to control blood pressure, prevented the increased atherosclerosis.
While acute stress actually improves our brain's attention and increases our capacity to store important and life-protecting information, for example, a source of danger, chronic stress dampens our ability to keep track of information and places. Chronic stress does this by impairing excitability of nerve cells and by promoting atrophy of nerve cells in the hippocampus, a region of the brain that is important for spatial and verbal memory.
For the immune system, which is controlled by the nervous system and by circulating hormones, chronic stress suppresses the ability of the immune system to do its job. This, once again, is in contrast to acute stress. Acute stress actually helps the immune system handle a pathogen by causing immune cells to move out of the bloodstream and into tissues where they are needed. Chronic stress, however, impairs not only the ability of the immune system to relocate immune cells but also the ability of those cells to do their job of recognizing and responding to the pathogenic agent.
Whatever the cause may be, protecting your body against over-exposure to stress hormones is as important to the body as the ability to mount an adequate allostatic response in the first place. Either type of imbalance in allostasis qualifies under the definition of "allostatic load." People with long-term histories of persistent and relatively small elevations or deficiencies in stress hormone levels may show accelerated progress toward pathophysiology and disease. In the case of excess hormone production, these disorders include atherosclerosis, obesity, type 2 diabetes and cognitive impairment. For relative hormone insufficiency, the pathophysiology includes autoimmune and inflammatory disorders, chronic pain and chronic fatigue.
It is important to use behavioral coping skills to control over-production of stress hormones in challenging situations. This includes seeking social support, counting to ten and resisting an intemperate reaction or simply withdrawing from a situation rather than risking a destructive confrontation.
In dealing with the type of allostatic load involving hormone over-production, it is important to use behavioral coping skills to control over-production of stress hormones in challenging situations. This includes seeking social support, counting to ten and resisting an intemperate reaction or simply withdrawing from a situation rather than risking a destructive confrontation. Behavioral coping also includes engaging in health promoting behaviors, such as regular moderate exercise and a healthy diet with moderate food intake and controlled alcohol intake. It is also important to learn to see situations as a challenge and an opportunity, rather than as disasters about to happen. If this sounds like an admonition to "positive thinking" it is exactly that. These types of behaviors represent a first line of defense against the development of allostatic load.
In the case of relative hormone deficiency, there are experimental programs to treat with low dose glucocorticoids in the case of chronic fatigue syndrome and chronic pain but these have had mixed results. Admittedly, the medical community is still not certain how to treat these conditions.
Clearly, doctors of all types are involved in providing advice, counseling and/or psychotherapy aimed at helping patients deal in a more healthy way with the many stressors of life. Interestingly, different psychotherapeutic approaches might address more efficient and less costly allostasis in different ways. For example, cognitive therapy focuses on better labeling of the stimuli in the environment so that the same stimuli are subsequently interpreted in a less threatening, arousing way. On the other hand, behavioral or exposure therapy focuses on keeping the individual in a threatening environment long enough to allow the neuroendocrine and autonomic systems to handle the situation. For example, a person with a fear of flying might be treated with air travel simulations until their body learns to "cope" with the fear. Whatever you do, it is important that the right psychotherapeutic" strategy appropriate for you and your "nervous system" be selected.
A classic example is fever. It's not clear whether a doctor should treat it with medicine or let it run its course. Fever is often a good and natural response ("adaptive") to an acute infectious agent but the person with a fever must pay a significant price in "feeling sick." It now appears that the treatment of a fever might actually delay recovery from an infectious process. Similar questions are raised about the use of antiinflammatories and whether they might sometimes interrupt a healing process.
Now, we even know that stress can sometimes cause us problems by making us react too little.
So, treating an allostatic response might be hazardous. Interestingly, some people with infectious episodes go on to develop the Chronic Fatigue Syndrome (CFS) which is often characterized by intermittent feverishness and malaise like that occurring with an infection, even though the person has no infection. It appears that this is a disorder where an inappropriate "allostatic" response is being made and this includes an insufficiency of the production of stress mediators like cortisol. Treatment will likely center on how to make the allostatic responses mounted by the CFS patient more appropriate. As we have already noted, this may include giving low dose cortisol treatment to supplement what the body produces.
Another situation often confronting doctors is whether or not to treat a patient for the symptoms arising in the wake of the loss of a loved one. Bereavement is characterized by many, but clearly not all, of the symptoms of depression, such as depressed mood, tearfulness and changes in sleep and appetite. Yet, many regard bereavement to be a restorative, healing and even necessary part of the process of losing a loved one. However, some bereaved people experience symptoms of such severity and length that treatment for depression is pursued.
Developing clear and useful standards for differentiating healing from unhealthy bereavement is an ongoing but difficult job and a clear example of the types of judgments facing the doctor who is going to treat the mismatches of challenge and allostatic response.
In the future, we will need to develop better detectors for environmental stressors (infectious, interpersonal, etc.), better detectors for allostatic response and better ways of determining whether a response is turned on too much or too little or is of too long or too short a duration. This allostatic framework, however, will help guide you and your doctor as you together decide whether you're sick or stressed out