Models of Stress

Research on stress and disease in sociology, psychology, and epidemiology paralleled work on modernization and disease in anthropology. By the late 1970s, a rough synthesis had emerged that could be used in the development of research models that would be useful cross-culturally. The term "stress" can be used to as a shorthand description for a general area of inquiry. Stress research or the stress model takes as subject-matter the direct link of thought, emotion, and behavior to physiologic changes and hence to disease. In early usage, the term referred to a specific physiologic pathway, although contemporary physiologic research recognizes that there are multiple pathways hormonally mediated by the hypothalamo-pituitary-adrenal axis, the hypothalamo-pituitary-gonadal axis, and the hypothalamo-pituitary-thyroid axis (as well as others; Worthman, 1999).

From the standpoint of social and culture theory, the aim was to identify factors that could be anticipated to be reliably associated with the activation of efforts at adaptation on the part of individuals, that would in turn be associated with a particular pattern of physiologic responses, that in turn could lead to sustained disease. Until recently, the major empirical link made was from social-environmental factors to disease, with the intervening links of physiology posited by analogy with laboratory experiments. More recently, some techniques have been developed that make it possible to measure hormonal mediators in the field and link them to disease outcomes (Panter-Brick & Worthman, 1999). The opportunity to study the physiologic mediators of the stress process is an important addition to the research in this area. At the same time, a principal aim of research continues to be the identification and measurement of factors in the social environment that tax individual adaptive capabilities.

There are two broad classes of social factors thought to influence risk of disease. Stressors are those factors that are (or are understood to be) problematic for individuals. These are events or circumstances that must be dealt with at some level for life to proceed smoothly. Stressors can be further divided into two categories. Acute stressors are typically events that occur suddenly with little warning, or if they are anticipated, their occurrence is limited in time. Chronic stressors are problematic circumstances that persist through time. Both chronic and acute stressors are associated with an increased risk of disease.

A second broad category of social factors can be referred to as resistance resources. Resistance resources are factors that enable the individual to avoid, withstand, or alter the stressful events and circumstances to which she is exposed. These again can be divided into two categories. Social support refers to the help or assistance that an individual can anticipate or receive by virtue of her membership in a network of social relationships. Coping styles refer to relatively stable individual dispositions to approach stressful circumstances in particular ways. On the one hand, individuals may actively seek out ways of coping with the occurrence of a stressor; on the other hand, individuals may more passively withdraw from a stressful circumstance and attempt to emotionally alter the meaning of the stressor.

One of the more influential models of the way in which these factors influence disease risk is the stress buffering model. It is argued that stresses in life are a more-or-less ubiquitous part of human existence, yet not everyone succumbs to the effects of stressors. Rather, individuals, even though they may be exposed to stressors, may not suffer the effects of those stressors because of their available social or psychological resources. Stressors will then have two different patterns of associations with disease risk. On the one hand, where resources are low, stressors will have a substantial effect on disease risk. On the other hand, where resources are high, individuals may be insulated from the stressor effects. That is, resistance resources may buffer the effects of stressors. Actually, one of the most influential papers in this area was also authored by Cassel (1976), who turned to stress models of this kind in search of operationally more explicit ways of examining stress processes.

The question then became one of how this general model might be applied in various ethnographic settings. Scotch (1963) was one of the first anthropologists to look at blood pressure from an explicit stress model. He compared samples of Zulu in South Africa, one sample living in a traditional homeland, the other living in an urban area. He found a variety of factors to be associated differently with high blood pressure in each area. For example, women who were past childbearing age were more likely to have high blood pressure in the rural area, while they were more likely to have low blood pressure in the urban area. Similarly, individuals who were members of Christian churches were more likely to have high blood pressure in the rural area, and low blood pressure in the urban area. Scotch interpreted this pattern of associations as evidence of stress, due to the incongruity between behaviors and context. Women past childbearing age experienced a loss of valued social status in the rural area, while they were relieved of onerous economic burdens in the urban area. Similarly, members of Christian churches were viewed with a certain suspicion in the more traditional and conservative rural areas, while in the urban areas this opened up the possibility of greater social participation. While Scotch's work is still broadly interpretive (i.e., there is little operational specificity to support his arguments), his research was groundbreaking and set the stage for later studies of blood pressure.

Dressler (1982) developed a specific model of stress and culture change on the island of St. Lucia, in the eastern Caribbean, using the theoretical synthesis described above, and building on Scotch's work. By the mid-1970s, St. Lucia had experienced some 20 years of very modest, but sustained economic growth as a result of innovations in the banana industry, which in turn spurred development in other areas. An increasing exposure of people to media representations of North American and European middle-class lifestyles accompanied this growth. The accumulation of consumer goods (e.g., radios, stereos, imported furniture) was emerging as a primary definer of local social status. At the same time, the real potential for increasing incomes to sustain such lifestyle aspirations did not grow at the same rate (economic growth may trickle down, but it does so very slowly and very incompletely). This meant that for a substantial portion of the population the economic resources necessary to fuel the high status lifestyle were absent, although this hardly altered lifestyle aspirations. Drawing on theories of status inconsistency, Dressler argued that individuals who presented themselves in mundane social interaction as having attained the valued lifestyles, but who did not have the economic standing consistent with that claim, would not receive confirmation of their status claims by others. This inconsistency in social status, referred to as "lifestyle incongruity," was predicted be a chronically stressful circumstance which would be associated with higher blood pressure, and this hypothesis was confirmed (after controlling for age, sex, and the body mass index).

At the same time, the social and psychological resources that could support coping with stressful circumstances were investigated. In St. Lucia, social support took a very specific form, relative to patterns of family and household formation that have been well described for the West Indies. It is unusual for persons to marry prior to beginning a family, and frequently individuals will have children by two or more other people. This practice, along with a high solidarity among adult siblings, links individuals into large networks of households. Because individuals are expected to support their offspring, both "inside" and "outside" the household, and because of adult sibling solidarity, there are flows of material resources among households with these links. Dressler hypothesized that this comprised a social support system that would buffer the stressful effects of lifestyle incongruity, and this hypothesis was also supported.

These results were replicated in a variety of settings (Bindon, Knight, Dressler, & Crews, 1997; Dressler, 1993; McGarvey, 1999). It is worth noting, however, what varied, more and less, across cultural contexts. Generally speaking, lifestyle incongruity could be opera-tionalized in very similar ways across different contexts, and had very similar effects. This is because the process leading to status incongruence of this sort is a function of how capitalist markets make their way into local settings. The market for mass-produced goods and services, and the social value attached to those goods and services, is global in nature, as is the generally slow growth of local economies. Therefore, this aspect of the process looks very much the same in different places. Social support systems, however, are rooted in social structure within each local setting, and are therefore much more variable. In a sense, then, the status incongruence/social support model represents an examination of how processes of globalization intersect with local social structures in terms of cardiovascular health outcomes.

There are, however, ways in which stressors can be culturally modified. A good example of this can be found in Janes's (1990) study of blood pressure among Samoan migrants to northern California. Culture change in Samoa accelerated with the advent of World War II, and initiated a process of migration from Samoa to Hawaii and the mainland United States. Like so many migrants, Samoans in the United States were able, in part, to re-create village life in the context of urban centers such as San Francisco. This re-creation could, however, lead to difficulties. On the one hand, there were Samoans who continued their aspirations for status along traditional dimensions, especially seeking chiefly statuses (matai) and a leadership role in the extended family. On the other hand, there were Samoans who sought status along more traditional American middle-class dimensions, especially in terms of achieving white-collar occupational status. In the former case there is a relatively heavy financial investment to achieve status. In the latter case the investment is more in the form of increased educational qualifications. Janes created two measures of status incongruence, one "internally" oriented toward the Samoan community, and the other "externally" oriented toward the American community. Each of these was associated with an increased risk of high blood pressure.

With respect to social supports, in Samoa the extended family would be the appropriate unit for examining social support. But migration to the United States makes the extended family unit a source of difficulty as well, especially because of the economic demands that lead people to focus more on the nuclear family as the relevant social unit in American urban centers. Therefore, Janes argued that it is only a subset of extended family relationships (again, in this case adult siblings) that can truly be considered a source of support in times of felt need. Consistent with these ethnographic observations, higher support from siblings buffered the effects of stressors on blood pressure.

These studies, incorporating insights from the stress model, proved to be very effective in moving medical anthropologists beyond the modernization paradigm in studying the risk of cardiovascular disease. It is important to emphasize that all these studies were embedded within ethnographic research on these communities. Without careful attention to local meaning and local understanding, it would have been impossible to identify relevant variables in each setting and to develop culturally appropriate measures of those variables for inclusion in multi-variate models. Ethnography provides the context for the research.

At the same time, this research is somewhat limited in its investigation of cultural influences in these processes. Like so much anthropological research, the concept of culture provides a general interpretive context for the research, leading investigators to identify certain kinds of social and behavioral factors as important because of the meaning attached to those factors in those specific settings. But what about more direct effects of culture? This is what Cassel and his collaborators were arguing for in their earlier papers, but the methodological and conceptual tools were not available for making those ideas operational. In more recent work, using innovations in culture theory and method, researchers have returned to these questions.

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