Stress
What is Stress?
Stress is a negative emotional experience accompanied bypredictable biochemical, physiological, cognitive, and behavioral changes thatare directed either toward altering the stressful event or accommodating to its effects.
What Is a Stressor?
Initially, researchers focused on stressful events themselves, called stressors. Such events include noise, crowding, a bad relationship, a round of job interviews, or the commute to work. Each stressful experience may be stressfulto some people but not to others. Whereas one person might find the loss of a job highly stressful, another might see it as an opportunity to try a new field, and as a challenge rather than a threat. How a potential stressor is perceived substantially determines whether it will be experienced as stressful.
Person-Environment Fit
Stress is the consequence of a person's appraisal processes: the assessment of whether personal resources are sufficient to meet the demands of the environment. Stress, then, is determined by person-environment fit.
(1) When a person's resources are more than adequate to deal with a difficult situation, he or she may feel little stress. (2) When the individual perceives that his or her resources will probably be sufficient to deal with the event but only at the cost of great effort, he or she may feel a moderate amount of stress. (4) When the individual perceives that his or her resources will probably not suffice to meet an environmental stressor, he or she may experience a great deal of stress.
Theoretical Contributions to the Study of Stress
Fight or Flight
Cannon proposed that, when an organism perceives a threat, the body is rapidly aroused and motivated via the sympathetic nervous system and the endocrine system. This concerted physiological response mobilizes the organism to attack the threat or to flee; hence, it is called the fight-or-flight response.
Selye's General Adaptation Syndrome
Another important early contribution to the field of stress is Hans Selye's (1956, 1976) work on the general adaptation syndrome. Although Selye initially explored the effects of sex hormones on physiological functioning, he became interested in the stressful impact his interventions seemed to have. Accordingly, he exposed rats to a variety of prolonged stressors-such as extreme cold and fatigue-and observed their physiological responses. To his surprise, all stressors, regardless of type, produced essentially the same pattern of physiological responding. In particular, they allIed to an enlarged adrenal cortex, shrinking of the thymus and lymph glands, and ulceration of the stomach and duodenum. Thus, whereas Cannon's work explored adreno-medullary responses to stress-specifically, catecholamine secretion-Selye's work more closely explored adreno-cortical responses to stress.
From these observations, Selye (1956) developed his concept of the general adaptation syndrome. He argued that, when an organism confronts a stressor, it mobilizes itself for action. The response itself is nonspecific with respect to the stressor; that is, regardless of the cause of the threat, the individual will respond with the same physiological pattern of reactions. Over time, with repeated or prolonged exposure to stress, there will be wear and tear on the system.
The general adaptation syndrome consists of three phases. In the first phase, alarm, the organism becomes mobilized to meet the threat. In the second phase, resistance, the organism makes efforts to cope with the threat, as through confrontation. The third phase, exhaustion, occurs if the organism fails to overcome the threat and depletes its physiological resources in the process of trying.
The substantial impact of Selye's model on the field of stress continues to be felt today. One reason is that it offers a general theory of reactions to a wide variety of stressors over time. As such, it provides a way of thinking about the interplay of physiological and environmental factors. Second, it posits a physiological mechanism for the stress-illness relationship. Specifically, Selye believed that repeated orprolonged exhaustion of resources, the third phase of the syndrome, is responsible for the physiological damage that lays the groundwork for disease. In fact, prolonged or repeated stress has been implicated in disorders such as cardiovascular disease, arthritis, hypertension, and immune-related deficiencies.
Criticisms of the General Adaptation Syndrome
First, it assigns a very limited role to psychologicalfactors, and researchers now believe that the psychological appraisal of events is important in thedetermination of stress. A second criticism concerns the assumption that responses to stress are uniform. There is evidence that not all stressors produce the same endocrinological responses. A third criticism concerns the fact that Selye assessed stress as an outcome, such that stress is evident only when the general adaptation syndrome has run its course. Despite these limitations and reservations, Selye's model remains a cornerstone of the field of stress.
Tend-and-Befriend
It argues that, during the time that responses to stress evolved, males and females faced somewhat different adaptive challenges and that female response to stress evolved so as to protect not only the self but also offspring.
Like the fight-or-flight mechanism, tend and-befriend may depend on underlying biological mechanisms. In particular, the hormone oxytocin may have significance for female responses to stress. Oxytocin is a stress hormone, rapidly released in response to at least some stressful events, and its effects are especial1y modulated by estrogen, suggesting an important role in the responses of females.
In support of the theory, there is evidence that females are consistently more likely than males to respond to stress by turning to others. Mothers' responses to offspring during stress also appear to be different from those of fathers in ways encompassed by the tend-and-befriend theory.
Psychological Appraisal and the Experience of Stress
Primary Appraisal:maintains that, when individuals confront a new or changing environment, they engage in a process of primary,!ppraisal to determine the meaning of the event.
"Harm" is the assessment of the damage that has already been done by an event.
"Threat" is the assessment of possible future damage that may be brought about by the event. Thus, the man who has just lost his job may anticipate the problems that loss of income will create for him and his family in the future.
Finally, events may be appraised in terms of their "challenge," the potential to overcome and even profit from the event. For example, the man who has lost his job may perceive that a certain amount of harm and threat exists, but he may also see his unemployment as an opportunity to try something new.
Secondary Appraisal:Secondary appraisal is the assessment of one's coping abilities and resources and whether they will be sufficient to meet the harm, threat, and challenge of the event. Ultimately, the subjective experience of stress is a balance between primary and secondary appraisal. When harm and threat are high and coping ability is low, substantial threat is felt. When coping ability is high, stress may be minimal.* Cognitive responses to stress include outcomes of the appraisal process! such as specific beliefs about the harm or threat an event poses and beliefs about its causes or controllability. Cognitive responses also include involuntary stress responses such as distractibility and inability to concentrate; performance disruptions on cognitive tasksand intrusive, repetitive, or morbid thoughts.
The Physiology of Stress
Two interrelated systems are heavily involved in the stress response. They are the sympathetic-adreno-medullary (SAM) system and the hypothalamic-pituitary-adreno-cortical (HPA) axis.
Sympathetic Activation: Sympathetic arousal stimulates the medulla of the adrenal glands, which, in turn, secrete the catecholamine, epinephrine and nor epinephrine. These effects result in the cranked up feeling we usually experience in response to stress. Sympathetic arousal leads to increased blood pressure, increased heart rate, increased sweating, and constriction of peripheral blood vessels, among other changes.
HPA Activation: The hypothalamus releases corticotrophin releasing factor (CRF), which stimulates the pituitary gland to secrete adreno-corticotropic hormone (ACTH), which, in turn, stimulates the adrenal cortex to release glucocorticoids. Of these, cortisol is especially significant. It acts to conserve stores of carbohydrates and helps reduce inflammation in the case of an injury. It also helps the body return to its steady state following stress.
Individual Differences in Stress Reactivity:People vary in their reactivity to stress: Some people show very small reactions to stressful circumstances, whereas others show large responses. Reactivity is the change in response to stress that may occur in autonomic, neuro-endocrine, and/or immune responses to stress.
Physiological Recovery Processes:Recovery processes following stress are also important in the physiology of the stress response. In particular, the inability to recover quickly from a stressful event may be a marker for the cumulative damage that stress has caused. Researchers have paid special attention to the cortisol response--particularly prolonged cortisol responses that occur under conditions of high stress.
Allostatic Load:Allostatic load builds up, which is defined as the physiological,costs ofchronic exposure to fluctuating or heightened neural or neuro-endcrine response that results from repeated or chronic stress. But over time this response may give way to exhaustion, leading to cumulative damage to the organism.
What Makes Events Stressful?
Dimensions of StressfulEvents:
Negative Events: Negative events are more likely to produce stress than are positive events. Many events have the potential to be stressful because they present people with extra work or special problems that may tax or exceed their resources. Shopping for the holidays, planning a party, coping with an unexpected job promotion, and getting married are all positive events that draw off substantial time and energy. Nonetheless, these positive experiences are less likely to be reported as stressful than are undesirable events, such as getting a traffic ticket, trying to find a job, coping with a death in the family, or getting divorced.
Negative events show a stronger relationship to both psychological distress and physical symptoms than do positive ones. This may be because only stressful events that have negative implications for the self-concept produce potential or actualloss of self-esteem ,
UncontrollableEvents: Uncontrollable or unpredictable events are more stressful than controllable or predictable ones. Negative events such as noise, crowding, or discomfort might seem to be stressful, but stress research consistently demonstrates that uncontrollable events are perceived as more stressful than controllable ones. When people feel that they can predict, modify, or terminate an aversive event or feel they have access to someone who can influence it, they experience it as less stressful, even if they actually do nothing about it.
Ambiguous Events:Ambiguous events are often perceived as more stressfulthan are clear-cut even Is. When a potential stressor is ambiguous, a person has no opportunity to take action. He or she must instead devote energy to trying to understand the stressor.
Overload:Overloaded people are more stressfulthan are people with fewer tasks to perform. People who have too many tasks in their lives report higher levels of stress than do those who have fewer tasks.
Can People Adapt to Stress?
If a stressful event becomes a permanent or chronic part of their environment, will people eventually habituate to it or will they develop chronic strain? Will it no longer cause them distress, drain psychological resources, or lead to symptoms of illness? The answer to this question depends on the type of stressor, the subjective experience of stress, and which indicator of stress is considered.
Physiological Adaptation: Low-level stress may produce habituation in most people, but with more intense stress, as the allostatic load model suggests, damage from chronic stress can accumulate across multiple organ systems.
Recently, researchers have looked at immune responses that are associated with long-term stressful events to address the question of habituation. Herbert and Cohen found that exposure to a long-term stressful event was significantly related to poorer immune functioning. What this research suggests is that physiological habituation may not occur or may not be complete when stressors are long-term and that the immune system may particularly be compromised by long-term stress.
Psychological Adaptation: Most people are able to adapt psychologically to moderate or predictable stressors, at first, any novel, threatening situation can produce stress, but such reactions often subside over time. Research on the effects of environmental noise and crowding also indicates few or no long-term adverse health or psychological effects, suggesting that most people simply adapt to these chronic stressors.
So, people (and animals) show signs of both long-term strain and habituation to chronically stressful events. Most people can adapt moderately well to mildly stressful events; however, it ma-y-be difficult or impossible for them to adapt to highly stressful events, and already-stressed people may be unable to adapt to even moderate stressors. Moreover, even when psychological adaptation may have occurred, physiological changes in response to stress may persist.
Must A Stressor Be Ongoing To Be Stressful?
Anticipating Stress: The anticipation of a stressor can be at least as stressful as its actual occurrence, and often more so. Consider the strain of anticipating a confrontation with a friend or worrying about a test -that will occur the next day. Sleepless nights and days of distracting anxiety testify to the human being's capacity for anticipatory distress.
Aftereffects ofStress: The effects of stress often persist long after the stressful event itself is no longer present. The so-called aftereffects of stress can be even more devastating than the stressful event itself. Aftereffects of stress have been observed in response to a wide range of stressors, including noise, high task load, electric shock, crowding, and laboratory-induced stress.
There is some evidence that stressors can produce deleterious aftereffects on social behavior as well as on cognitive tasks. Several studies have found that, when people arc exposed to avoidable stressful events, such as noise or crowding, they are less likely to help someone in distress when the stressor is over.
The fact that stressful events produce aftereffects should not be surprising. Even simply arriving late to an exam may leave the heart racing for half an hour, interfering with effective performance. Exposure to a stressor over a longer period of time may have cumulative adverse effects, so that reserves are drained and resistance breaks down when a person has to cope with a stressful event. Unpredictable and uncontrollable stressful events appear to be particularly likely to produce deleterious aftereffect.
Helplessness: Other long-term costs of stress include the helplessness and learned helplessness that can result. The centrality of stress to helplessness has already been noted, as stress occurs when the demands of the environment are perceived to exceed a person's resources. The idea behind learned helplessness is that repeated efforts to exert control in situations that fail to achieve their desired effects lead to longer-term, wide-ranging helplessness.
Cognitive deficits include the fact that helpless people may fail to learn new responses that could help them. Emotional costs may occur, in that learned helplessness can lead to depression.
How Stress Has Been Studied
We now turn to the methods that health psychologists have used for measuring stress and assessing its effects on psychological and physical health. In particular, we look at the measurement of stressful life events, daily hassles, chronic strain, and stress in the workplace and the home.
As one considers the ways in which stress and its effects have been studied, it is useful to remember that stress can affect psychological and physical health directly, as by changes in physiology, or indirectly, through health-relevant behaviors such as health habits (smoking, drinking) and use of health services (delay behavior, non-adherence to medication use).
Studying Stress in the Laboratory
The acute stress consistently finds that, when people are induced to perform stressful tasks, they show strong indications of sympathetic activity, such as increases in heart rate, blood viscosity, and blood pressure, and strong neuro-endocrine responses suggestive of increased HPA activity, such as increased cortisol responses.
Use of the acute stress paradigm has proven invaluable for understanding what kinds of events produce stress and how reactions to stress are influenced by factors such as personality, social support, and the presence of chronic stress in a person's life. For example, responses to acute stress among those who are also chronically stressed tend to be more exaggerated than among those not going through chronic stress as well.