Both homeostasis and allostasis, whole body regulatory concepts, function in our lexicon as integrative terms for understanding physiological/behavioral systems. They reflect our need to understand how internal viability is maintained in a changing environment (see also Mrosovsky, 1990; Bauman,
2000). Allostasis is tied to the central nervous system as it supervenes in the assessment and regulation of bodily states (Sterling and Eyer, 1988; Schulkin et al., 1994).
One impetus for the idea of allostasis was linked to concern about our social world. In a paper by Eyer and Sterling (1977) entitled "Stress-Related Mortality and Social Organization," a major portion was a critique of our society and the onset of a variety of disease states. Sterling and Eyer (1988) and others pointed to the detrimental sequelae of "chronic arousal" (Chrousos and Gold, 1992, 1998; McEwen and Stellar, 1993; Schulkin et al., 1994; Goldstein, 1995a, b). Sterling and Eyer were concerned about widespread chronic fatigue due to overstimulation. They endorsed practices that enhance calmness, such as transcendental meditation and community-based attachments.
One result of chronic arousal is the overactivation of allostatic anticipatory mechanisms, feedforward mechanisms, and eventual allostatic overload (McEwen, 1998a, b; Koob and Le Moal,
2001). The concept of allostasis emphasizes multiple systems in both the adaptive phase and the decline in pathology. The gradual decline of end-organ systems reflects allostatic overload, through their chronic overactivation and exaggerated expression. Moreover, long periods of physiological regulation are emphasized under allostatic regulation, in addition to cephalic innervation of physiological functions (within the rubric of allostatic regulation). In addition, the concept of allostasis was invoked to account for the way in which one lives; whether one smokes, drinks, or uses psychotropic drugs; how one eats; whether one is defending against deadly viruses.
Allostasis and Cortisol—The Hormone of Energy Metabolism
Cortisol, as I have indicated, has permissive, stimulatory, sup-pressive, and preparative functions in orchestrating bodily viability to acute challenges (Ingle, 1952; Munck et al., 1984; McEwen, 1998a, b; Sapolsky et al., 2001). Glucocorticoids regulate cardiovascular, metabolic, and neural adaptive functions in the short-term context in a wide variety of ways (Sapolsky et al., 2000).
Social rank is one instance in which cortisol is clearly linked to behavioral expression. Social ranking and attachment have profound effects on internal physiology (Herbert, 1993; Gunnar, 1998; Sapolsky, 2000). In addition, cognitive factors, such as determining what is a real threat from what might not be, can determine cortisol levels; baboons who were less able to determine the real from the not real had higher levels of cortisol and perhaps chronic arousal (figure C.1; Sapolsky, 2000). But more generally, baboons with elevated levels of cortisol were linked to a number of appraisal responses to danger; those with higher cortisol tended to be less likely to differentiate threatening and neutral stimuli, initiate a fight that can be won, differentiating winning and losing a fight, and less likely to express displaced aggression after losing a fight (Sapolsky, 2001). In rats, chronic elevated levels of glucocorticoids along with elevated levels of central CRH are associated with lower social dominance and defeat (Albeck et al., 1997).
Socioeconomic status and a mother's vulnerability to depression affect the levels of cortisol in children (figure C.2; Lupien et al., 2000). For example, children in Montreal with the lowest socioeconomic status had the highest level of cortisol (Lupien et al., 2000). Some factors, however, are unknown, including:
Male baboons that are less able to determine the reality of a competitive situation have higher basal levels of cortisol (Sapolsky, 2000).
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