Objective: To determine whether there is a relationship between depressive symptoms and cortisol assessed at first morning awakening, 6 PM, and 9 PM in a population-based sample of midlife women. If this relationship is not linear, we aim to test whether this relationship is nonlinear, only present in those with more severe depressive symptoms, better accounted for by diurnal slope, or only apparent under uncontaminated conditions.
Methods: We investigated the cross-sectional association between cortisol and depressive symptoms, assessed by the Center for Epidemiological Studies Depression scale (CES-D) in 408 midlife women (45.7% African Americans, 54.3% white; mean age, 50.4 years) participating in the Chicago site of the Study of Women's Health Across the Nation.
Results: Diurnal cortisol slope is significantly flatter for women with higher CES-D scores than for less depressed women (p < .05 for the interaction). This relationship remains significant even after adjusting for age, smoking status, race, education, income, menopausal status, hormone replacement therapy, body mass index, medications, and wake time, as well as possibly contaminating factors, including physical activity, smoking, eating, or caffeine or alcohol consumption before saliva collection. Results using depression assessed categorically (CES-D cutoff ≥16) were similar to those using continuous depression in both unadjusted and adjusted analyses (p = .005 for the interaction of CES-D by time).
Conclusions: In this population-based sample of midlife women, greater depressive symptoms were associated with a significantly flatter diurnal cortisol slope than those with fewer symptoms, even after adjusting for covariates and possibly contaminating behaviors.