The role of stress-induced cortisol in the relationship between depression and decreased bone mineral density

Background This study was designed to test the hypothesis that cortisol mediates the relationship between bone density and depression in postmenopausal women. Methods Nineteen women aged 52–79 who had been assessed for bone mineral density by dual-energy x-ray absorptiometer (DEXA) were evaluated for depression and anxiety. Diurnal and stress-induced measures of salivary cortisol were obtained during the following week and at a laboratory session involving a speech task. Results Nine volunteers reported depression while 10 were never depressed. Ever depressed women had significantly lower total lumbar and right femur DEXA Z scores than never depressed (t(17) = 2.5, p = .019 and t(17) = 2.06, p = .05, respectively). Ever depressed women demonstrated a significant increase in salivary cortisol (area under the curve (AUC) = 27.83, SD = 37.64) compared to never depressed women (AUC = -13.34, SD = 19.55) (t(17) = -3.041, p = .007) during a psychological challenge. There were significant inverse relationships between salivary cortisol AUC values and bone density Z scores at every measured bone site. Mediation analyses suggest that 51 – 67% of the association between depression and bone density could be attributed to stress-induced changes in cortisol. Conclusions Cortisol hypersecretion in response to stress may, in part, explain the impact of depression on bone density in post-menopausal women.