Cortisol and the course of depressive symptoms: The SMART-Medea Study
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Depression and dysregulation of the HPA-axis often co-occur, but the nature of this relationship is complex, and it is still unclear what the direction of causation is. We examined the influence of cortisol levels on the course of depressive symptoms for 10 years follow-up. Within the SMART-Medea study, analyses were performed in 674 patients with symptomatic atherosclerotic disease (mean age 62 ± 9 years). There were 7 salivary cortisol measures (4 measures of morning cortisol, 2 of evening cortisol and 1 of cortisol after dexamethasone were conducted). Depressive symptoms were assessed with the Patient Health Questionnaire-9 (PHQ-9) at baseline and every 6 months during 10 years of follow-up. Generalized Estimating Equation (GEE) models were used to assess the association between cortisol levels (morning cortisol, evening cortisol, and cortisol after dexamethasone) with depressive symptoms at multiple time points during follow-up. Interaction terms between respective cortisol levels and time was included to examine if depressive course differed according to baseline cortisol levels. The GEE analyses showed no significant interactions between respective cortisol levels and time, indicating no different course of depressive symptoms according to baseline cortisol levels. Analyses were adjusted for age, sex, vascular risk factors and use of anti-depressants and benzodiazepines. Excluding patients with major depressive disorder did not change the results. This means that dysregulation of the HPA-axis does not influence the course of depression. It is possible that the course of depression influences cortisol levels instead.