Diurnal Cortisol Interacts With Stressful Events to Prospectively Predict Depressive Symptoms in Adolescent Girls

Purpose The aim of present study was to test the diathesis-stress model of depression using baseline cortisol, prospective assessment of depression symptoms, and stressful life events. Methods The sample consisted of 527 adolescent girls aged 13.5–15.5 years without major depressive disorder. At baseline, saliva samples were collected at waking, 30 minutes after waking, and 8 P.M. on 3 consecutive days. Diurnal cortisol was indexed by cortisol awakening response (CAR) and area under the curve with respect to ground (AUCg). Stressful events during the preceding interval and current depressive symptoms were assessed 18 months following baseline. Results Stressful events and the interaction of CAR or AUCg with stressful events predicted depressive symptoms at 18 months, even after controlling for baseline depressive symptoms. Specifically, in the face of high levels of stress, baseline blunted CAR or smaller AUCg were associated with future depressive symptoms. This was more apparent for CAR than AUCg. The effect was reversed at low levels of stress, with heightened CAR associated with more severe depressive symptoms. Conclusions Blunted CAR and less daily cortisol output at baseline appear to accentuate the depressogenic effects of stressful events after 18 months, consistent with the diathesis-stress model of hypothalamic-pituitary-adrenal axis function in depression.