A Lifecourse Perspective on Cumulative Stress and Its Effects on Depression in Adulthood

Purpose: There are well-established links between stress and mental health (Thakkar, 2000; Sachs-Ericsson, et al., 2009). In particular, studies have demonstrated clear relationships between stress and depression (Brown & Harris, 1987; Dohrenwend, 2000; Hammen, 1999). At the same time, the health effects of chronic stress have received much attention, with researchers concluding that chronic stress causes psychological and physiological “wear and tear” (McEwen, 2007; Olstad, et al. 2001), affecting what Hobfoll (1996) termed “spirals of loss,” wherein accumulation of stress renders individuals less able to effectively respond. Yet, current literature on stress and mental health rarely takes the chronicity of stress into account. Due in part to a lack of longitudinal studies with which we might examine stress at multiple, critical timepoints, we have relatively little information about how stress occurs over the lifecourse as well as about how stress, as it accumulates over time, affects later depression.

Methods: This study uses longitudinal data collected from 356 individuals within the time-points of childhood, adolescence, and adulthood, to examine first the relationships between stress at each time-point, and then the long-term mental health effects of chronic stress. We determined 6 domains of stress that were similar among all three time points: neighborhood, economic, family conflict, household substance abuse, emotional/mental problems in household, household trouble with police. We first explored the relationships of different types of stress among time-points. Then, we tested the hypothesis that chronic stress would raise the overall risk of adult depression, after controlling for childhood maltreatment and depression in adolescence. To move from separate indices of stress at each individual time point so that we could examine the cumulative effects of stress over time, we dichotomized the time-point specific cumulative stress scores into high frequency of stress– those in the top 25 percentile and low frequency of stress– those in the bottom 75 percentile. We added the dichotomous scores to create a count of how many periods of high stress were experienced throughout the lifecourse – 0, 1, 2, or 3. Path models were used to test the effects of chronicity of stress, after controlling for gender and accounting for the effects of childhood maltreatment and adolescent depression.

Results: Multiple domains of high stress were correlated between the most proximal time-points; there were significant correlations between childhood and adolescence and between adolescence and adulthood for economic stress, family conflict, household substance abuse, and trouble with police. Chronicity of stress was a significant independent predictor of adult depression (ß= .204, p=.000), after accounting for the effects of adolescent depression and childhood maltreatment on adult depression (ß= .352, p=.000 and ß= .084, p=.094, respectively). Variables in the model explained 24% of the variance in adult depression (r²= .239; p= .000).

Implications: Findings demonstrate that stress may be constant between critical developmental periods, and that chronicity of stress significantly raises the risks for depression. Results illustrate the need to assess for chronic stress, and to develop interventions that address how stress accumulates throughout the lifecourse.