the factors that influence whether and when these role combinations have adverse or beneficial effects on mental and physical health merits research attention (Repetti et al., 1989). For example, female caregivers for older demented adults experienced long-term changes in immunity and health as a result of combining this demanding role with existing home and work responsibilities (Kiecolt-Glaser et al., 1991). Nurses scoring higher on job demands had higher ambulatory blood pressure and heart rate during the workday and higher epinephrine in the evening, and married nurses had higher nighttime cortisol levels than did unmarried women (Goldstein et al., 1999). These findings suggest that both high work demands and a combination of job demands and role demands at home have identifiable potentially adverse effects on neuroendocrine and physiological profiles. These effects were stronger the longer these women had worked. For a superb discussion of women's work roles, their impact on mothers and their children and health consequences, all from an evolutionary perspective, see Hrdy (1999).
As these research examples attest, intensely stressful environmental conditions (e.g., the aftermath of a natural disaster, unemployment), geographic areas of intense chronic stress (such as crowded neighborhoods), and life domains in which intense change is occurring (e.g., changing patterns of combining work and family) present special opportunities to identify predisease pathways that, to date, have been understudied. These acutely and chronically stressful conditions create alterations in underlying physiology and neuroendocrine responses that may be precursors to adverse health and mental health conditions. Using such naturally occurring conditions and events as laboratories for investigating predisease pathways and identifying who is most at risk for adverse health effects can lead to substantial progress in understanding the parameters of predisease states, the mechanisms by which they develop, and subsequent progression to disease.
The preceding discussions of prenatal and early life risk factors, psychological states, behavioral factors, and environmental stressors address a wide array of precursors to illness and disease, focused largely on early life. As yet these diverse literatures have not been linked with cumulative physiological risk, as illustrated by the concept of allostatic load, in later life. Indeed, research on allostatic load has been conducted primarily in samples of adults and the aged. Thus, an important direction for future research on predisease pathways is to connect these diverse early life risks (biological, behavioral, psychological, environmental) to subsequent life course trajec-