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The physiological and psychological responses to situations or events that disturb the equilibrium of an organism.

While there is little consensus among psychologists about the exact definition of stress, it is agreed that stress results when demands placed on an organism cause unusual physical, psychological, or emotional responses. In humans, stress originates from a multitude of sources and causes a wide variety of responses, both positive and negative. Despite its negative connotation, many experts believe some level of stress is essential for well-being and mental health.

Stressors—events or situations that cause stress— can range from everyday hassles such as traffic jams to chronic sources such as the threat of nuclear war or over-population. Much research has studied how people respond to the stresses of major life changes. The Life Events Scale lists these events as the top ten stressors: death of spouse, divorce, marital separation, jail term, death of close family member, personal injury or illness, marriage, loss of job through firing, marital reconciliation, and retirement. It is obvious from this list that even good things—marriage, retirement, and marital reconciliation—can cause substantial stress.

When presented with a stressful event or situation, the process of cognitive appraisal determines an individual's response to it. One option—to judge the stressor as irrelevant—would cause little disturbance and thus little stress. For example, a high school student who does not plan to attend college will experience much less stress during the Scholastic Assessment Test (SAT) than a student who wants to attend a top university, even though both are in the same situation. Another option is recognizing the stressor as disturbing, yet positive. Retirement or marriage could fit into this category. The judgment that a situation truly is stressful would cause the most disturbance and thus the most stress. For example, few people would consider a serious traffic accident as anything less than stressful. The magnitude of resulting stress from any

Source: "What Are the Leading Causes of Stress?" In Science and Technology Desk Reference. Edited by The Carnegie Library of Pittsburgh Science and Technology Department. Detroit: Gale Research, Inc. 1993, p. 415. (Stanley Publishing. Reproduced with permission.)
Death of spouse
Marital separation
Jail term or death of close family member
Personal injury or illness
Loss of job due to termination
Marital reconciliation or retirement
Change in financial state

situation generally depends upon a person's perceived ability to cope with it. If the stress is predictable—a scheduled dentist appointment, for example—it usually causes less stress. A person's ability to control the stressor also can mitigate its effects. A strong network of social support undermines the magnitude of stress in most situations.

Reactions to stress, then, vary by individual and the perceived threat presented by it. Psychological responses may include cognitive impairment—as in test anxiety, feelings of anxiety, anger, apathy, depression, and aggression. Behavioral responses may include a change in eating or drinking habits. Physiological responses also vary widely. The "fight or flight" response involves a complex pattern of innate responses that occur in reaction to emergency situations. The body prepares to handle the emergency by releasing extra sugar for quick energy; heart rate, blood pressure, and breathing increase; muscles tense; infection-preventing systems activate; and hormones are secreted to assist in garnering energy. The hypothalamus, often called the stress center of the brain, controls these emergency responses to perceived life-threatening situations.

Research has shown that stress is a contributing factor in a majority of disease cases. A relatively new area of behavioral medicine, psychoimmunology, has been developed to study how the body's immune system is affected by psychological causes like stress. While it is widely recognized that heart disease and ulcers may result from excess stress, psychoimmunologists believe many other types of illness also result from impaired immune capabilities due to stress. Cancer, allergies, and arthritis all may result from the body's weakened ability to defend itself because of stress.

Coping with stress is a subject of great interest and is the subject of many popular books and media coverage. One method focuses on eliminating or mitigating the effects of the stressor itself. For example, people who experience extreme stress when they encounter daily traffic jams along their route to work may decide to change their route to avoid the traffic, or change their schedule to less busy hours. Instead of trying to modify their response to the stressor, they attempt to alleviate the problem itself. Generally, this problem-focused strategy is considered the most effective way to battle stress. Another method, dealing with the effects of the stressor, is used most often in cases in which the stress is serious and difficult to change. Major illnesses, deaths, and catastrophes like hurricanes or airplane crashes cannot be changed, so people use emotion-focused methods in their attempts to cope. Examples of emotion-focused coping include exercise, drinking, and seeking support from emotional confidants. Defense mechanisms are unconscious coping methods that help to bury, but not cure, the stress. Sigmund Freud considered repression—pushing the source of stress to the unconscious— one way of coping with stress. Rationalization and denial are other common emotional responses to stress.

Further Reading

Tanner, Ogden. Stress. New York: Time-Life Books, 1976.

Additional topics

Psychology EncyclopediaPsychological Dictionary: Perception: early Greek theories to Zombie