Measuring Stress in Humans: A Practical Guide for the Field available in Hardcover, Paperback
Measuring Stress in Humans: A Practical Guide for the Field
- ISBN-10:
- 1107407583
- ISBN-13:
- 9781107407589
- Pub. Date:
- 09/13/2012
- Publisher:
- Cambridge University Press
- ISBN-10:
- 1107407583
- ISBN-13:
- 9781107407589
- Pub. Date:
- 09/13/2012
- Publisher:
- Cambridge University Press
Measuring Stress in Humans: A Practical Guide for the Field
Buy New
$65.99Overview
Product Details
| ISBN-13: | 9781107407589 |
|---|---|
| Publisher: | Cambridge University Press |
| Publication date: | 09/13/2012 |
| Series: | Cambridge Studies in Biological and Evolutionary Anthropology , #49 |
| Pages: | 284 |
| Product dimensions: | 5.98(w) x 9.02(h) x 0.59(d) |
About the Author
Gary D. James is Director of the Institute for Primary and Preventative Health Care, and Professor of Nursing and Anthropology at Binghamton University.
Read an Excerpt
Measuring Stress in Humans
Cambridge University Press
978-0-521-84479-6 - Measuring Stress in Humans: A Practical Guide for the Field - by Gillian H. Ice
Excerpt
Introduction
In recent years, interest in the study of stress has expanded, particularly in the disciplines of anthropology and human biology where the focus of research has drifted toward evaluating the adaptive biological, cultural and psychological responses to stressors inherent in everyday living. Field studies of stress in these disciplines have been conducted across a wide continuum ofcontexts. These range from an assessment of the stress of “modernization” where biological and cultural responses of populations undergoing rapid industrialization/Westernization are examined, e.g. James et al. (1985), to the responses of people facing novel, new environments in modern, Western societies, such as occur in nursing homes (Ice et al., 2002).
Biologically, in studying the stress response, measurements can be made at any of several junctures in the psychophysiological pathways between stressful stimuli and adaptive or pathological outcomes. Measures include emotional/behavioral responses, hormonal variation in the sympathetic adrenal medullary system (SAMS), hormonal variation in the hypothalamic pituitary adrenal axis (HPA), physiological changes in the cardiovascular system and enhanced immune responses. The choice of the most appropriate measure will be determined by a combination of the goals of research, the population of interest and practical concerns. In addition to the particular stress marker(s) chosen for a study, the appropriate sampling strategy and design must be determined. These range from group comparisons of a one-time measure, to ecological momentary assessments, to multiple measures evaluated in a longitudinal design. Some study designs used in stress research require special analytic strategies and sophisticated statistical approaches.
While stress markers themselves are common outcome measures, the ultimate goal in stress research is to determine the relationships between stress and health or stress and adaptation. To this end, several conceptual models have been proposed across a variety of disciplines. It is the intent of this chapter to first provide an overview of these models as well as the tools and instruments used to evaluate the stress experience by researchers in the various disciplines, and then to introduce an integrated model in which stress is considered a process by which a stimulus elicits an emotional, behavioral and/or physiological response, which is conditioned by an individual's personal, biological and cultural context (Figure 1.1).
Definitions of stress and their origins
Stress research can be confusing as there are a multitude of definitions which are often not equivalent. The term “stress” has been used to refer to at least three different components of the stress process: 1) the input or stimuli, 2) processing systems, including both physiological and psychological and 3) the output or stress response, e.g. rise in blood pressure (Mason, 1975; Levine and Ursin, 1991). Different disciplines have focused on different aspects of the stress process. Table 1.1 provides a general guide of different approaches by discipline.
Early research on the physiological processes related to stress has been described by Walter Cannon (Cannon, 1914), the author of the “flight or fight syndrome.” He also coined the term “homeostasis” to describe the process of maintaining internal stability in the face of environmental change (Cannon, 1932). This term does not mean something fixed and unchanging, but a relatively constant, complex, well coordinated and usually stable condition. Cannon was also interested in determining the specific mechanisms of response to changes in the external environment, which allowed for optimal bodily function. He showed that there are specialized sensory nerves to communicate the state of the rest of the body to the brain, that the brain is able to detect non-optimal internal states, and that the brain can call a variety of mechanisms into play to compensate correctly. Finally, he noted that failure to maintain homeostasis could result in tissue damage or death, and he was among the first to examine the challenges of psychologically meaningful stimuli and the impact of moods (Cannon, 1929, 1932).
Hans Selye popularized the concept of “stress” and many researchers trace the origin of its study and definition to Hans Selye and his 1936 paper, “A syndrome produced by diverse nocuous agents” (Selye, 1936). In this paper, he described stress as a non-specific response of the body to “noxious stimuli.” Selye's concept described a physiological response to physical and physiological stimuli, described as stressors (Selye, 1946). Selye later named and elaborated on the process as the general adaptation syndrome (Selye, 1946). This syndrome has three stages: 1) alarm reaction, 2) stage of resistance and 3) stage of exhaustion. In the alarm stage, the body reacts to a stimulus by activating the hypothalamic pituitary adrenal (HPA) axis. The resistance stage signals successful adaptation to the stimulus. Exhaustion occurs when exposure to stimuli is prolonged. Selye believed that the body's stores of glucocorticoids (the output of the HPA axis) were depleted. Most researchers now believe that the body does not deplete stores of glucocorticoids but that prolonged exposure to a stressor results in suppression of the immune system and wear and tear of several body systems, which then places individuals at risk of a variety of disease outcomes.
While Selye and biomedical researchers conducted their research on physical and physiological stressors in animal models, several investigators starting looking at the impact of psychosocial stressors in humans. The initial focus of these investigations was traumatic or major life events. Many credit Adolf Meyer and Harold Wolff in the 1930s and 1940s for early development of research examining stressful life events and illness (Rahe, 1989; Cohen et al., 1997). Meyer suggested that physicians should record life events as part of their medical examination while Wolff went on to describe the association between life events and illness (Cohen et al., 1997). One of the first published scales created to measure life events, “The Social Readjustment Rating Scale” (Holmes and Rahe, 1967) has become the foundation upon which most current life events scales are based. While these researchers were looking at humans, they were still working from a Selyen model of a non-specific response to stressors.
Stress research focused on major life events through the 1960s with researchers further expanding the kinds of events that might be considered stressful. As it started to become clear that there were individual differences in the response to such events, Lazarus and colleagues developed a theory of stress which emphasized appraisal and coping in the late 1960s and 1970s. Lazarus has argued in multiple publications that the “stimulus-centered perspective” of life events approach and the physiological approaches of Selye and Cannon were too simplistic (Lazarus, 1984; Lazarus and Folkman, 1984; Lazarus, 1999). Lazarus and colleagues suggested that the best way to view the stress process is as a transaction between the person and environment (Lazarus, 1984; Lazarus and Folkman, 1984; Lazarus, 1999). The impact of any potential stimulus is determined by an individual's appraisal and coping. Within this transaction, an individual goes through a cognitive assessment to determine if a particular circumstance is a threat and if s/he has the resources or coping skills to meet the demand placed upon him/her by the threat (Lazarus and Folkman, 1984). Lazarus and Folkman define coping as, “constantly changing cognitive and behavioral efforts to manage specific external and/or internal resources of the person” (Lazarus and Folkman, 1984, p. 141). In addition to emphasizing the importance of appraisal and coping Lazarus has suggested that we shift our focus from major life events to daily hassles (Lazarus, 1984, 1999). From this cognitive theoretical approach, there may be limitless types of transactions between the person and environment depending on the context and the person's age, culture and experience. While psychologists were expanding the model of stress, the Selyen model still had a great impact on future biomedical and neurological research (Elliot and Eisdorfer, 1982). As Selye maintained that the stress response was non-specific (i.e. did not vary by stressor), the stressors chosen by biomedical researchers using animal models were often based on convenience rather than research question (Elliot and Eisdorfer, 1982). The concept of a non-specific response has since been questioned as a number of researchers have demonstrated variation in response to different stressors (Mason, 1975). Mason (1975) cited several studies which demonstrate that the HPA axis response to stressors varies with the type of stressor and the experimental conditions. He further pointed out that many of the “physical stressors” used in animal experiments have a psychological component. For example, in his own research on starvation in monkeys, the HPA response was significantly diminished when monkeys were fed non-nutrient placebo food (Mason, 1974). The placebo acted to minimize the psychological effect of sudden deprivation. Mason was one of the first to cross the disciplinary boundaries by incorporating psychological models of stress in his biological models. Cassel (1976) further pointed out that the Selyen concept of a non-specific response led many to suggest that there is such a thing as a “stress state” or “stress disease.” He suggested, as many have now come to believe, that stress does not produce a specific disease but rather places people in a state that makes them more susceptible to a range of diseases. He suggested that “psychosocial processes acting as ”conditional stressors”™ will, by altering the endocrine balance of the body, increase susceptibility of the organism to direct noxious stimuli, i.e. disease agents” (Cassel, 1976, p. 109). Both Mason and Cassel were influential in getting future researchers to think of stress as a process rather than a simple stimulus-response relationship suggested by biomedical researchers and those in the life-event arena.
Pearlin and colleagues (Dohrenwend and Pearlin, 1982; Pearlin, 1989) further criticized the life events and “stimulus–response” approaches on a number of accounts. First, they questioned the theory that all change is harmful and suggested that only change that is undesirable, unscheduled, non-normative and uncontrollable is harmful. Second, they suggested that the life-events approach treats events as if they occur in a vacuum without consideration of the socioeconomic context in which they occur. Further, they critiqued the instruments for measuring exposure to life events as a conflation of acute events with ongoing stressors. Pearlin suggested that health may be impacted not by the individual “major” event but by the “continuing circumstances in which the event is embedded” (Pearlin, 1989, p. 244). For example, if an individual forecloses on his/her house, s/he was likely to have experienced problems of continuous poverty and debt prior to the actual foreclosure. Pearlin did not suggest that life events are unimportant to the stress process, merely, that “some events under some conditions are powerful stressors that affect people's lives directly and indirectly” (Pearlin, 1989, p. 245). Pearlin emphasized the importance of looking at chronic stressors which he called strains. These were defined as “relatively enduring problems, conflicts and threats that many people face in their daily lives” (Pearlin, 1989, p. 245). His research particularly emphasized the importance of role strains which are problems connected to the social roles which people fill. Most importantly, Pearlin suggested that we should not look at chronic stressors or major life events in a vacuum as they may come together to produce stress in a number of ways (Pearlin, 1983). Life events may lead to chronic stressors or result from chronic stressors and they can interact and provide meaning for one another. While Lazarus focused on cognitive appraisal as a mediator of the stress process, Pearlin discussed the importance of social values in mediating the impact of a stressor. These social values “regulate the effects of experience by regulating the meaning and importance of the experience” (Pearlin, 1989, p. 249).
Lazarus, who emphasizes the individualistic aspect of the stress process, cautions against the socio-cultural approach to the stress process in which the impact of social structure or culture results in or mediates stress (Lazarus, 1999). By examining the stress process in this manner, Lazarus and Folkman argue that generalizations based on such analyses simplify our understanding of the process and distill a dynamic process into a static one in which people are treated as “carbon copies” as opposed to individual cognitive and emotional beings (Lazarus and Folkman, 1984). However, by examining social forces or social context, Pearlin is not really suggesting that individuals are carbon copies but that they do exist in a social context which should be considered when examining the stress process.
Dressler has been very influential in bringing cultural context into stress research (Dressler, 1991, 1995; Dressler and Bindon, 1997; Dressler and Bindon, 2000). In fact, he argues that culture has influence on multiple components of the stress process. Cultural context influences meaning of stressors, patterns of stressors and coping resources. Further, culture can be a stressor or it can be a mediator. His work on lifestyle incongruity and cultural consonance (further explained in Chapter 2) has had a tremendous impact on stress research within anthropology and human biology. These elegant models connect the individual process of stress with the social and cultural context, in a sense fusing the models of Lazarus and Pearlin.
Human Biologists (o Biological Anthropologists) have a history of looking at environmental stressors as a source of human variation. They often take the wider perspective that stressors are anything that take the body away from homeostasis and thus, by default, stress becomes a disruption in homeostasis. However, historically human biologists have approached stress in a very Selyen way. The traditional focus on adaptation to environmental stressors has carried over into the way that social stressors are often examined. Thus, human biologists have often started with a potential stressor and compared individuals exposed to those who are not. Often a “stress hormone” or health outcome is used to determine if the two groups differ in their level of stress. If there is a difference, this confirms that the potential stressor is indeed a stressor. Unfortunately, this research often left out notions of appraisal or socio-cultural context. With the maturing of stress research in human biology, models have become more complex and involve more of the stress process.
In 1988, Peter Sterling and Joseph Eyre introduced the concept of allostasis, literally “achieving stability through change” in order to provide a logical structure for understanding the ever-shifting integrated biobehavioral, endocrinological and physiological systems of the body that promote adaptation and drive natural selection (Sterling and Eyer, 1988). For example, were blood pressure to remain constant throughout the day, individuals would have difficulty responding to their own changing activities and other environmental variations. However, because it is part of an allostatic system, blood pressure will vary continuously to adapt the individual to the changing circumstances. Because it continuously changes, the individual does not have a single “homeostatic” blood pressure state per se, but rather has many stable states, which are directly related to the many and ever-changing internal and external environmental conditions to which the individual must adapt. The multiple stable states of blood pressure differentiate this physiological system from other bodily homeostatic systems such as those that maintain tissue pH. The HPA and SAMS axes also act as allostatic systems (McEwen and Stellar, 1993; McEwen, 1998a,b). Some have suggested that because the concept allostasis unifies the physiology of acute and long-term adaptations and stress responses as well as their outcomes into a single process, it should replace the stress concept (McEwen, 2002). As part of this argument, McEwen (McEwen and Stellar, 1993; McEwen, 1998a,b) has introduced the concept of allostatic load. While allostasis is critical to adaptation and survival, “allostatic load” is defined as “the price the body pays over long periods of time for adapting to challenges” (McEwen, 2001, p. 44). McEwen and colleagues have created an index of allostatic load and applied it to the health outcomes of participants in the MacArthur Aging Studies. To measure allostatic load, indicators of “system failure” (e.g. high blood pressure, large waist to hip ratios, elevated urinary epinephrine and cortisol, etc.) were tallied. The index was calculated from the number of indicators in which a participant's measurements fell in the uppermost (4th) quartile of the population distribution (Seeman et al., 1997a). This index of allostatic load predicted declines in cognitive and physical functioning, cardiovascular disease and mortality (Seeman et al., 1997a,b; Karlamangla et al., 2002).
In many ways, the concept of allostasis can be seen as a new spin on the old Selyen concept of stress. However, recently Schulkin (2004) edited a volume entitled Allostasis, Homeostasis, and the Costs of Physiological Adaptation in which a spectrum of physiological and biobehavioral processes were recast and evaluated from the perspective of allostasis. Based on the discussions in this volume, it is quite possible that the concept of allostasis may join homeostasis as the foundation for future understanding of the relationship between stress and adaptation.
© Cambridge University Press