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Stress is a term that refers to the sum of the physical, mental, and emotional strains or tensions on a person. Feelings of stress in humans result from interactions between persons and their environment that are perceived as straining or exceeding their adaptive capacities and threatening their well-being. The element of perception indicates that human stress responses reflect differences in personality as well as differences in physical strength or health.

A stressor is defined as a stimulus or event that provokes a stress response in an organism. Stressors can be categorized as acute or chronic, and as external or internal to the organism. The Diagnostic and Statistical Manual of Mental Disorders ( DSM-IV-TR ) defines a psychosocial stressor as "any life event or life change that may be associated temporally (and perhaps causally) with the onset, occurrence, or exacerbation [worsening] of a mental disorder."

Stress affects the lives of most adults in developed countries in many ways. It is a major factor in rising health care costs; one public health expert maintains that 90% of all diseases and disorders in the United States are stress-related. Stress plays a part in many social problems such as child and elder abuse , workplace violence, juvenile crime, suicide , substance addiction , "road rage," and the general decline of courtesy and good manners. Stress also affects the productivity of businesses and industries. One nationwide survey found that 53% of American workers name their job as the single greatest source of stress in their lives. Furthermore, the overall cost of medical care, time lost from work, and workplace accidents in the United States comes to over $150 million per year.

The neurobiology of stress

One way to understand stress as a contemporary health problem is to look at the human stress response as a biologically conditioned set of reactions that was a necessary adaptation at earlier points in human evolution, but is less adaptive under the circumstances of modern life. Hans Selye (1907-1982), a Canadian researcher, was a pioneer in studying stress. Selye defined stress, in essence, as the rate of wear and tear on the body. He observed that an increasing number of people, particularly in the developed countries, die of so-called diseases of civilization, or degenerative diseases, which are primarily caused by stress. Selye also observed that stress in humans depends partly on people's evaluation of a situation and their emotional reaction to it; thus, an experience that one person finds stimulating and exciting—for example, bungee jumping—would produce harmful stress in another.

The stress response

In humans, the biochemical response to acute stress is known as the "fight-or-flight" reaction. It begins with the activation of a section of the brain called the hypothalamic-pituitary-adrenal system, or HPA. This system first activates the release of steroid hormones, which are also known as glucocorticoids. These hormones include cortisol, the primary stress hormone in humans.

The HPA system then releases a set of neurotransmitters known as catecholamines, which include dopamine, norepinephrine, and epinephrine (also known as adrenaline). Catecholamines have three important effects:

  • They activate the amygdala, an almond-shaped structure in the limbic system that triggers an emotional response of fear.
  • They signal the hippocampus, another part of the limbic system, to store the emotional experience in longterm memory.
  • They suppress activity in parts of the brain associated with short-term memory, concentration, and rational thinking. This suppression allows a human to react quickly to a stressful situation, but it also lowers ability to deal with complex social or intellectual tasks that may be part of the situation.

In reaction to stress, heart rate and blood pressure rise, and the person breathes more rapidly, which allows the lungs to take in more oxygen. Blood flow to the muscles, lungs, and brain may increase by 300–400%. The spleen releases more blood cells into the circulation, which increases the blood's ability to transport oxygen. The immune system redirects white blood cells to the skin, bone marrow, and lymph nodes; these are areas where injury or infection is most likely.

At the same time, nonessential body systems shut down. The skin becomes cool and sweaty as blood is drawn away from it toward the heart and muscles. The mouth becomes dry, and the digestive system slows down.

The relaxation response

After the crisis passes, the levels of stress hormones drop and the body's various organ systems return to normal. This return is called the relaxation response. Some people are more vulnerable to stress than others because their hormone levels do not return to normal after a stressful event. An absent or incomplete relaxation response is most likely to occur in professional athletes and in people with a history of depression.

Physical effects of chronic stress

In chronic stress, the organ systems of the body do not have the opportunity to return fully to normal levels. Different organs become under- or overactivated on a long-term basis. In time, these abnormal levels of activity can damage an organ or organ system.

Cardiovascular system

Stress has a number of negative effects on the heart and circulatory system. Sudden stress increases heart rate, but also causes the arteries to narrow, which may block the flow of blood to the heart. The emotional effects of stress can alter the rhythm of the heart. In addition, stress causes the release of extra clotting factors into the blood, which increases the risk of a clot forming and blocking an artery. Stress also triggers the release of fat into the bloodstream, which temporarily raises blood cholesterol levels. Lastly, it is thought that people who regularly have sudden increases in blood pressure due to mental stress may over time suffer injuries to the inner lining of their blood vessels.

Gastrointestinal system

The effects of chronic stress on the gastrointestinal system include diarrhea, constipation, bloating, and irritable bowel syndrome. Although stress is not the direct cause of either peptic ulcers or inflammatory bowel disease, it may predispose people to develop ulcers and worsen flareups of inflammatory bowel disease.

Stress is the cause of abnormal weight loss in some people and of weight gain in others, largely from stress-related eating. It is thought that stress related to the physical and emotional changes of puberty is a major factor in the development of eating disorders.

Reproductive system

Stress affects sexual desire in both men and women and can cause impotence in men. It appears to worsen the symptoms of premenstrual syndrome (PMS) in women. Stress affects fertility, in that high levels of cortisol in the blood can affect the hypothalamus, which produces hormones related to reproduction. Very high levels of cortisol can cause amenorrhea, or cessation of menstrual periods.

Stress during pregnancy is associated with a 50% higher risk of miscarriage. High stress levels on the mother during pregnancy are also related to higher rates of premature births and babies of lower than average birth weight; both are risk factors for infant mortality.

Musculoskeletal system

Stress intensifies the chronic pain of arthritis and other joint disorders. It also produces tension-type headaches, caused by the tightening of the muscles in the neck and scalp. Research indicates that people who have frequent tension headaches have a biological predisposition for converting emotional stress into muscle contraction.


The physical effects of stress hormones on the brain include interference with memory and learning. Acute stress interferes with short-term memory, although this effect goes away after the stress is resolved. People who are under severe stress become unable to concentrate; they may become physically inefficient, clumsy, and accident-prone. In children, however, the brain's biochemical responses to stress clearly hamper the ability to learn.

Chronic stress appears to be a more important factor than aging in the loss of memory in older adults. Older people with low levels of stress hormones perform as well as younger people in tests of cognitive (knowledgerelated) skills, but those with high levels of stress hormones test between 20% and 50% lower than the younger test subjects.

Immune system

Chronic stress affects the human immune system and increases a person's risk of getting an infectious illness. Several research studies have shown that people under chronic stress have lower than normal white blood cell counts and are more vulnerable to colds and influenza. Men with HIV infection and high stress levels progress more rapidly to AIDS than infected men with lower stress levels.

Stress and mental disorders

DSM-IV-TR specifies two major categories of mental disorders directly related to stress—the post-traumatic syndromes and adjustment disorders. Stress is, however, also closely associated with depression, and can worsen the symptoms of most other disorders.

Post-traumatic disorders

Post-traumatic stress disorder (PTSD) and acute stress disorder (ASD) are defined by their temporal connection to a traumatic event in the individual's life. The post-traumatic disorders are characterized by a cluster of anxiety and dissociative symptoms, and by their interference with the patient's normal level of functioning. Magnetic resonance imaging (MRI) studies have shown that the high levels of sustained stress in some PTSD patients cause demonstrable damage to the hippocampus. Excessive amounts of stress hormones in brain tissue cause the nerve cells, or neurons, in parts of the hippocampus to wither and eventually die. One group of Vietnam veterans with PTSD had lost as much as 8% of the tissue in the hippocampus.

Substance abuse disorders

Stress is related to substance abuse disorders in that chronic stress frequently leads people to self-medicate with drugs of abuse or alcohol. Substance abuse disorders are associated with a specific type of strategy for dealing with stress called emotion-focused coping. Emotion-focused coping strategies concentrate on regulating painful emotions related to stress, as distinct from problem-focused coping strategies, which involve efforts to change or eliminate the impact of a stressful event. Persons who handle stress from a problem-oriented perspective are less likely to turn to mood-altering substances when they are under stress.

Adjustment disorders

DSM-IV-TR defines adjustment disorders as psychological responses to stressors that are excessive given the nature of the stressor; or result in impairment of the person's academic, occupational, or social functioning. The most important difference between the post-traumatic disorders and adjustment disorders is that most people would not necessarily regard those stressors involved in the latter disorder as traumatic. Adjustment disorder appear to be most common following natural disasters, divorce, becoming a parent, and retirement from work.

Causes of stress

The causes of stress may include any event or situation that a person considers a threat to his or her resources or coping strategies. A certain amount of stress is a normal part of life; it represents a person's response to inevitable changes in his or her physical or social environment. Moreover, positive events can generate stress as well as negative events. Graduating from college, for example, is accompanied by stress related to employment or possible geographical relocation and the stress of saying good-bye to friends and family, as well as feelings of positive accomplishment. Some researchers refer to stress associated with positive events as eustress.

Acute stress is defined as a reaction to something perceived as an immediate threat. Acute stress reactions can occur to a falsely perceived danger as well as to a genuine threat; they can also occur in response to memories. For example, a war veteran who hears a car backfire may drop to the ground because the noise triggers vivid memories, called flashbacks, of combat experience. Common acute stressors include loud, sudden noises being in a crowded space such as an elevator, being cut off in heavy traffic; and dangerous weather. Chronic stress is a reaction to a situation that is stressful but ongoing, such as financial worries or caring for an elderly parent. Modern life is stressful because changes in various areas of life have increased the number of acute and chronic stressors in most people's lives at the same time that they have weakened certain buffers or protections against stress.

Social changes

Social changes that have increased the stress level of modern life include increased population mobility and the sprawling size of modern cities. It is not unusual for adults to live hundreds of miles away from parents and siblings; and it is hard to make and keep friendships when people move every few years. In most large cities, many people live in apartment buildings where they do not know their neighbors. Social isolation and loneliness can produce chronic stress. A study done in Norway between 1987 and 1993 found that social support networks made a significant difference in lowering the impact of both acute and chronic stress on mental health.

Social scientists have observed that the increased isolation of married couples from extended families and friendship networks increases strains on the marriage. The rising divorce rate in the United States has been attributed in part to the loss of social supports that once helped to keep married couples together. The experience of divorce then adds to the stress level on the former spouses and the children, if any. A long-term study at the University of Pittsburgh has found that divorce is associated with a higher rate of premature death in men.

Economic changes

The rapid pace of change in manufacturing and other businesses means that few people will work at the same job for their entire career. In addition, corporate mergers and downsizing have weakened job security, thus producing chronic anxiety about unemployment in the minds of many employees. Many people work two jobs in order to make ends meet; and even those who work only one job often have to commute by car or train to their workplace. In many large American cities, traffic jams, cost of gasoline, and other problems related to commuting are a major factor in job-related stress. Another stress factor is sleep deprivation. Many people get only six or less hours of sleep each night even though the National Sleep Foundation estimates that most adults need 8–8-1/2 hours per night for good health. Fatigue due to sleep deprivation causes additional stress.

Lastly, economic trends have produced a "winner-take-all" economy in which the gap between the well-off and the average family is constantly widening. Socioeconomic status (SES) affects health in a number of ways. Persons of higher SES can afford better health care, are less likely to suffer from exposure to environmental toxins, and generally lead healthier lifestyles. In addition, chronic stress associated with low SES appears to increase morbidity and mortality among persons in these income groups.

Technological changes

Technology has proved to be a source of stress as well as a solution to some kinds of stress. Machines that help workers to be more productive also make their jobs more complicated and raise the level of demands on them. An office clerk in 2002 can produce many more letters per day than one in 1952, but is often expected to produce more elaborate, professional-looking documents as well as a higher number of them.

One specific technological development that has been singled out as a major stressor in modern life is the evolution of news reporting. For most of human history, people had to wait several days or even weeks to hear about the outcome of an election, a battle, or some other important event. Moreover, they usually heard only the news that affected their region or their country. Today, however, news is reported as soon as it happens, it is broadcast 24 hours a day, and it covers events around the world. This "communications overload," as it has been termed, is a source of genuine stress to many people, particularly when the newscast emphasizes upsetting or frightening events. It is not surprising that a common recommendation for lowering one's stress level is to cut down on watching television news programs. A team of physicians conducted telephone interviews following the events of September 11, 2001, in order to assess stress reactions in the general American population. The team found that the single most important factor was not geographical location relative to the attacks or educational level, but the amount of time spent watching televised reports of the attacks. The interviewers discovered that 49% of the adults had watched at least eight hours of television on September 11, and also that "extensive television viewing was associated with a substantial stress reaction."

Environmental changes

One significant source of stress in modern life is the cumulative effect of various toxic waste products on the environment. Studies of the aftermath of such environmental disasters as Three Mile Island and Chernobyl found that not only evacuees and people living in the contaminated area had high levels of emotional distress, but also cleanup workers and people living in nearby noncontaminated areas. In the case of Chernobyl, Russian physicians have reported a psychoneurological syndrome with several unexplained symptoms, including fatigue, impaired memory, muscle or joint pain, and sleep disturbances. The syndrome appears to be due to chronic emotional stress rather than radiation exposure.

Changes in beliefs and attitudes

Changes in beliefs that influence stress levels include the contemporary emphasis on individualism and a corresponding change in attitudes toward trauma. A number of observers have remarked that Western culture has moved away from its traditional high valuation of the family and community toward an increased focus on the individual. Some have called this trend the "Me First!" society—it emphasizes personal rights and entitlements rather than duties and responsibilities to others. It has, in the view of some physicians, encouraged people to dwell on trauma and its effects on them as individuals rather than to live up to more traditional ideals of composure and resilience in the face of distress.

Risk factors

Research indicates that some categories of people have a higher risk of stress-related illnesses and disorders:

  • Children have very little control over their environments. In addition, they are often unable to communicate their feelings accurately.
  • In elderly adults, aging appears to affect the body's response to stress, so that the relaxation response following a stressful event is slower and less complete. In addition, the elderly are often affected by such major stressors as health problems, the death of a spouse or close friends, and financial worries.
  • Caregivers of mentally or physically disabled family members.
  • Women in general.
  • People with less education.
  • People who belong to racial or ethnic groups that suffer discrimination.
  • People who live in cities.
  • People who are anger-prone. Chronic anger is associated with narrowing of the arteries, a factor in heart disease.
  • People who lack family or friends.
  • People who are biologically predisposed to an inadequate relaxation response.

Coping with stress

Coping is defined as a person's patterns of response to stress. Many clinicians think that differences in attitudes toward and approaches to stressful events are the single most important factor in assessing a person's vulnerability to stress-related illnesses. A person's ability to cope with stress depends in part on his or her interpretation of the event. One person may regard a stressful event as a challenge that can be surmounted while another views it as a problem with no solution. The person's resources, previous physical and psychological health, and previous life experience affect interpretation of the event. Someone who has had good experiences of overcoming hardships is more likely to develop a positive interpretation of stressful events than someone who has been repeatedly beaten down by abuse and later traumas.

Coping styles

The ways in which people cope with stress can be categorized according to two different sets of distinctions. One is the distinction between emotion-focused and problem-focused styles of coping, which was described earlier in connection with substance abuse. Problem-focused coping is believed to lower the impact of stress on health; people who use problem-focused coping have fewer illnesses, are less likely to become emotionally exhausted, and report higher levels of satisfaction in their work and feelings of personal accomplishment. Emotion-focused coping, on the other hand, is associated with higher levels of interpersonal problems, depression, and social isolation. Although some studies reported that men are more likely to use problem-focused coping and women to use emotion-focused coping, other research done in the last decade has found no significant gender differences in coping styles.

The second set of categories distinguishes between control-related and escape-related coping styles. Control-related coping styles include direct action, behavior that can be done alone; help-seeking, behavior that involves social support; and positive thinking, a cognitive style that involves giving oneself pep talks. Escape-related coping styles include avoidance/resignation, as in distancing oneself from the stressful event, and alcohol use. There appears to be no relationship between gender and a preference for control-related or escape-related coping.

Stress management

Stress management refers to a set of programs or techniques intended to help people deal more effectively with stress. Many of these programs are oriented toward job- or workplace-related stress in that burnout is a frequent result of long-term occupational stress. Most stress management programs ask participants to analyze or identify the specific aspects of their job that they find stressful, and then plan a course of positive action to minimize the stress. In general, the severity of job-related stress appears to be related to two factors: the magnitude of the demands being made on the worker, and the degree of control that she or he has in dealing with the demands. The workers who are most vulnerable to stress-related heart disease are those who are subjected to high demands but have little control over the way they do their job. In many cases, stress management recommendations include giving an employee more decision-making power.

Treatments for stress

There are a number of allopathic and alternative/complementary treatments that are effective in relieving the symptoms of stress-related disorders:

  • Medications may include drugs to control anxiety and depression as well as drugs that treat such physical symptoms of stress as indigestion or high blood pressure.
  • Psychotherapy, including insight-oriented and cognitive/behavioral approaches, is effective in helping people understand how they learned to overreact to stressors, and in helping them reframe their perceptions and interpretations of stressful events. Anger management techniques are recommended for people who have stress-related symptoms due to chronic anger.
  • Relaxation techniques, anxiety reduction techniques , breathing exercises, yoga , and other physical exercise programs that improve the body's relaxation response.
  • Therapeutic massage, hydrotherapy, and bodywork are forms of treatment that are particularly helpful for people who tend to carry stress in their muscles and joints.
  • Aromatherapy , pet therapy, humor therapy, music therapy, and other approaches that emphasize sensory pleasure are suggested for severely stressed people who lose their capacity to enjoy life; sensory-based therapies can counteract this tendency.
  • Naturopathic recommendations regarding diet, exercise, and adequate sleep, and the holistic approach of naturopathic medicine can help persons with stress-related disorders to recognize and activate the body's own capacities for self-healing.



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The American Institute of Stress. 124 Park Avenue, Yonkers, NY 10703. (914) 963-1200. Fax: (914) 965-6267. <> .

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See also Creative therapies ; Diets ; Nutrition and mental health

Rebecca J. Frey, Ph.D.

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