What are stress-related diseases?
The term “stress,” as it is used in the field of psychology, may be defined as the physical or psychological disturbance an individual experiences as a result of what that individual perceives to be an adverse or challenging circumstance. Four observations concerning this definition of stress should be made. First, stress is what the individual experiences, not the circumstance causing the stress (the stressor). Second, individuals differ in what they perceive to be stressful. What may be very stressful for one individual may not be at all stressful for another. Hans Selye, the researcher who did more than anyone else to make the medical community and the general population aware of the concept and consequences of stress, once noted that, for him, spending the day on the beach doing nothing would be extremely stressful. This difference in people’s perceptions is behind the familiar concept that events do not cause stress. Instead, stress comes from a person’s perception or interpretation of events.
Third, stress occurs in response to circumstances that are seen as negative, but stress may also arise from challenging circumstances, even positive ones. The well-known Social Readjustment Rating Scale developed by Thomas Holmes and Richard Rahe includes both positive and negative life events. A negative event, such as the death of a spouse, is clearly stressful; however, marriage, generally viewed as a positive life event, can also be stressful. Fourth, stressors can lead to stress-related disturbances that are psychological, physiological, or both. The psychological response is rather unpredictable. A given stressor may result in one individual responding with anger, another with depression, and another with a new determination to succeed.
The physiological response is more predictable. Beginning in the 1930s, Selye began studying the human response to stressors. Eventually he identified what he termed the general adaptation syndrome to describe the typical pattern of physical responses. Selye divided the general adaptation syndrome into three stages: alarm, resistance, and exhaustion.
The first stage begins when an individual becomes frightened, anxious, or even merely concerned. The body immediately undergoes numerous physical changes to cope with the stressor. Metabolism speeds up. Heart and respiration rates increase. The hormones epinephrine, norepinephrine, and cortisol are secreted. Sugar is released from the liver. The muscles tense. Blood shifts from the internal organs to the skeletal musculature. These and a host of other changes are aimed at helping the body cope, but the price paid for this heightened state of arousal typically includes symptoms such as headache, upset stomach, sleeplessness, fatigue, diarrhea, and loss of appetite. The body’s increase in alertness and energy is accompanied by a lowered state of resistance to illness.
Obviously, people cannot remain in the alarm stage for long. If the stressor is not removed, the body enters the resistance stage—a stage that may last from minutes to days or longer. During this stage, the body seeks to adapt to the stressor. The physical changes that occurred during the alarm stage subside. Resistance to illness is actually increased to above-normal levels. Because the body is still experiencing stress, however, remaining in this stage for a long period will eventually lead to physical and psychological exhaustion—the exhaustion stage.
Selye has noted that over the course of life, most people go through the first two stages many, many times. Such is necessary to adapt to the demands and challenges of life. The real danger is found in not eliminating the stressor. During the exhaustion stage, the body is very vulnerable to disease and in extreme cases may suffer collapse and death. Although later research has found subtle differences in the stress response, depending on the stressor involved, the basic findings of Selye have continued to be supported. In addition to the direct physiological effects of stress on the body, indirect effects may also lead to illness. For example, stress may cause or exacerbate behavioral risk factors such as smoking, alcohol use, and overeating.
Specific illnesses can also be caused or promoted by stress. For many years Americans have been aware of the relationship between stress and heart disease. The biochemical changes associated with stress lead to higher blood pressure, an increased heart rate, and a release of fat into the bloodstream. If the fat is completely consumed by the muscles through physical activity (for example, defending oneself from an attacker), no serious health consequences follow. If, however, a person experiences stress without engaging in physical activity (a more common scenario in Western culture), the fat is simply deposited on the walls of the blood vessels. As these fatty deposits accumulate, life is threatened.
The work of two cardiologists, Meyer Friedman and Ray Rosenman, is of particular importance to a discussion of heart disease and stress. Friedman and Rosenman demonstrated, based originally on personal observation and subsequently on clinical research, that there is a personality type that is particularly prone to heart disease. The personality type that is at the greatest risk was found to be one which is highly stressed—impatient, hostile, hard-driving, and competitive. They termed this a Type A personality. The low-risk person, the Type B personality, is more patient, easygoing, and relaxed.
Numerous studies have examined health based on the Type A-Type B concept. Virtually all have supported Friedman and Rosenman’s conclusions. One major report, however, did not; subsequent analysis of that report and other research generally has indicated that the aspects of the Type A personality that are threatening to one’s health are primarily the hostility, cynicism, and impatience, not the desire to achieve.
A newer area of research that is even more fundamental to understanding how stress is related to disease involves the immune system. As the physiological changes associated with stress occur, the immune system is suppressed. The immune system has two primary functions: to identify and destroy hazardous foreign materials called antigens (these include bacteria, viruses, parasites, and fungi) and to identify and destroy the body’s own cells that have undergone changes associated with malignancy. Thus, if the immune system is suppressed, the body is less able to detect and defend against a host of diseases. An example of this effect again involves research with laboratory rats. One such investigation involved placing tumor cells in the bodies of rats. Some of the rats were then exposed to an abundance of stress. Those that were given this treatment were less resistant to the cancer. Their tumors were larger, and they developed sooner than those found in the “low-stress” rats.
The recent growth of the field of psychoneuroimmunology focuses specifically on the chemical bases of communication between mind and body. Research in this area provides evidence that the body’s immune system can be influenced by psychological factors that produce stress. One study, for example, showed that during students’ examination periods, the levels of students’ antibodies that fight infections were lowest. Thus they were most vulnerable to illness at that most stressful time. Health centers confirm that students tend to report more illness during examination times.
As research continues, the number of specific diseases that can be linked to stress grows. A partial listing of stress-related diseases and disorders for which recent research is available would include acne, asthma, cancers (many types), colds, coronary thrombosis, diabetes mellitus, gastric ulcers, herpes simplex (types 1 and 2), human immunodeficiency virus (HIV) infection, hyperlipidemia, hypertension, infertility, irritable bowel syndrome (IBS), migraine headache, mononucleosis syndrome, rheumatoid arthritis, streptococcal infection, stroke, systemic lupus erythematosus, and tuberculosis.
Research has shown that stress may also play a role in depression, sleep disturbances, ovulation, and brain atrophy associated with Alzheimer’s disease. Stress as a cause of stomach ulcers has been essentially negated, with the discovery that these ulcers are generally caused by the bacterium Helicobacter pylori, which can be treated with antibiotics. However, stress may still play a role in decreasing the mucous lining of the stomach, which makes it more vulnerable to ulcer formation. Some experts feel that there is no illness that is not in some way influenced by stress.
Few, if any, of these physical problems are caused solely by stress. Many other factors influence risk, including genetic composition, gender, race, environmental conditions, and nutritional state. Nevertheless, stress is frequently an important factor in determining initial resistance as well as the subsequent course of a given disease.
Some individuals appear to live with many stressors yet generally avoid physical and psychological illness. Understanding why is important, because it can provide insight as to what the average person can and should do to lower stress levels. Dispositional factors (optimistic versus pessimistic, easygoing versus hard-driving, friendly versus hostile) are probably most important in determining a person’s stress level. The Type A-Type B research is an example of research demonstrating the influence of dispositional factors.
Research with twins has found that temperament is largely inborn; however, any individual can choose to be more optimistic, generous, and patient. Norman Cousins is often cited as an example of a person who decided to change his outlook and mental state to preserve his life. He had read Selye’s The Stress of Life (1956), which describes how negative emotions can cause physical stress and subsequent disease. Cousins, who had a rare and painful illness from which he was told he would most likely never recover, decided that if negative emotions could harm one’s health, then positive emotions could possibly return one’s health.
As Cousins describes his experience in Anatomy of an Illness as Perceived by the Patient (1979), he left his hospital room for a more pleasant environment, began trading massive doses of drugs for massive doses of vitamin C and a steady diet of television comedies and laughter, and decided to stop worrying. To the surprise of his medical team, his recovery began at once. Though this now-classic example is only anecdotal, the research on disposition and stress would support the assumption that Cousins’s decision to change his mental state and stop worrying—not his avoidance of traditional medical care—was a truly important influence.
A related area of research has investigated how psychological hardiness helps people resist stress. Studies by Suzanne Kobasa and her colleagues examined business executives who all had an obvious abundance of stressors in their lives. In comparing those hardy individuals who handled the stressors well with the nonhardy individuals, the researchers found that the two groups differed in three important but basic ways.
The first was commitment. Stress-resistant executives typically possessed a clear sense of values. They had clear goals and a commitment to those goals. Less hardy executives were more likely to feel alienation. The second was challenge. The hardy executives welcomed challenges and viewed change rather than stability as the norm in life. Their less healthy counterparts viewed change with alarm. The third factor was control. The hardy executives felt more in control of their lives. This aspect of Kobasa’s research overlaps with research conducted since the 1960s involving a concept known as the locus of control. People with an internal locus of control are those individuals who believe they are influential rather than powerless in controlling the direction of their lives. This area of research has also found that such a belief lowers stress.
Many studies have been conducted to examine the relationship between physical fitness and mental health. What has emerged from this heavily researched area is a clear conclusion: Exercise can lower stress levels. Though regular, sustained aerobic exercise is generally advocated, research has found that even something as simple as a daily ten-minute walk can have measurable beneficial effects. During exercise, there is a release of chemical substances, including neurotransmitters called endorphins. Endorphins act to decrease pain and produce feelings of well-being, somewhat like an opiate. Exposure to stress has been shown to increase the level of endorphins in the body. For example, studies were conducted with runners, one group using naloxone, a substance that blocks the effects of opiates, and the other group a placebo that had no effect on the body. After strenuous runs, those taking the placebo reported feelings of euphoria, sometimes known as runners’ high. Those taking naloxone reported no such feelings. During exercise, the body releases other chemicals, including dopamine, which is thought to act as an antidepressant. Thus there is abundant evidence of the stress-reducing benefits of exercise.
Another approach to reducing stress involves learning to evoke a physical relaxation response, a term coined by Harvard Medical School cardiologist Herbert Benson. Benson became intrigued by the ability of some people who practice meditation to lower their blood pressure, heart rate, and oxygen consumption voluntarily. He discovered that the process is not at all mystical and can be easily taught. The process involves getting comfortable, closing the eyes, breathing deeply, relaxing muscles, and relaxing the mind by focusing on a simple word or phrase.
Others are helped by using an electronic device that closely monitors subtle physiological changes. By observing these changes (typically on a monitor), a person can, for example, learn to slow down a heart rate. This is known as biofeedback training. Many other techniques and suggestions arising from research as well as common sense can lower stress. A strong social support system has been found to be very important; disciplining oneself not to violate one’s own value system is essential. Even having a pet that needs love and attention has been found to lower stress.
A general recognition that a relationship exists between mind and body is at least as old as the biblical Old Testament writings. Proverbs 17:22 reads, “A cheerful heart is good medicine,/ but a crushed spirit dries up the bones.” Hippocrates, generally considered the father of medicine, sought to understand how the body could heal itself and what factors could slow or prevent this process. He clearly perceived a relationship between physical health and what is now termed stress, though his understanding was shallow.
Several physiologists of the nineteenth century made contributions; however, it was not until the twentieth century that the classic studies of American physiologist Walter Bradford Cannon proved the link scientifically. Cannon and his student Philip Bard began their analysis of stress and physiological arousal to disprove the idea espoused by others, that emotion follows physiological arousal.
Cannon found a variety of stressors that led to the release of the hormones adrenaline and noradrenaline (or, properly now, epinephrine and norepinephrine). Heat, cold, oxygen deprivation, and fright all led to hormonal changes as well as a number of additional physiological adaptations. Cannon was excited about this discovery and impressed with the body’s remarkable ability to react to stressors. All these changes were aimed at preparing the body for what Cannon termed the fight-or-flight response. It was Selye’s task to build on Cannon’s work. His description of the reaction subsequently termed the general adaptation syndrome first appeared in a scientific journal in 1936. As knowledge of the stress concept began to spread, interest by the public as well as the research community increased.
Literally tens of thousands of stress research studies conducted throughout the world were completed during the last half of the twentieth century. Of particular importance was the discovery by three American scientists that the brain produces morphinelike antistress substances. The discovery of these substances, named endorphins, won the 1977 Nobel Prize for the scientists involved and opened a whole new area of research.
Research has shown that the brain itself produces neuropeptides, or brain message transmitters, that may also be produced by macrophages—white blood cells that attack viruses and bacteria. Because some forms of stress-reduction such as relaxation also seem to result in production of neuropeptides, if the brain could be caused to produce more of these substances, the immune system could be strengthened. The hope remains that someday an endorphin-type drug could be used to counter some of the unhealthy effects of stress, ensuring better health and longer lives. Better health and longer lives are available even today, however, for all people who are willing to make lifestyle changes based on current knowledge.
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