Hypothalamic-pituitary-adrenal axis activity in older persons with and without a depressive disorder

Background: Altered functioning of the hypothalamic-pituitary-adrenal axis (HPA-axis) has been associated with depression, but findings have been inconsistent. Among older depressed persons, both hyperactivity and hypo-activity of the HPA-axis were demonstrated. However, most studies were population-based studies, with single cortisol measurements, lacking insight into diurnal patterns of HPA-axis functioning. We aim to provide insight into functioning of the HPA-axis, assessed by various salivary cortisol samples, in depressed older adults and non-depressed controls.

Methods: Data were derived from the Netherlands Study of Depression in Older Persons. Cortisol levels of older persons without a lifetime diagnosis of depression and/or anxiety (n=109) were compared with older persons with a 6-month major depression diagnosis (n=311). ANCOVA analyses and random coefficient analysis on the four morning cortisol samples were performed. A possible U-shaped association between cortisol and depression status was examined.

Results: Depressed older persons showed higher morning cortisol levels at awakening (T1) and a less dynamic awakening response compared to non-depressed older persons. Dexamethasone suppression did not differ across groups. No U-shaped association between HPA-axis activity and depression was observed.

Conclusion: We demonstrated a hypercortisolemic state and a diminished ability to respond to the stress of awakening among depressed older persons. Previously it was shown, that hypercortisolemic states may indicate a lifelong biological vulnerability for depression. Our findings expand on previous literature by demonstrating that in older persons the HPA-axis may become less responsive to stress, culminating in a further dysregulation of the diurnal cortisol-rhythm, superimposed on - possibly lifelong - hypercortisolemic states.