Research published in Psychosomatic Medicine (2005;67, Supplement 1:S26–S28) explored the relationship between severe depression and dysfunction of the hypothalamic–pituitary–adrenal (HPA) axis.
One method used to assess HPA axis regulation is the dexamethasone suppression test. Dexamethasone is a synthetic glucocorticoid that normally suppresses cortisol production by inhibiting the release of adrenocorticotropic hormone (ACTH) from the pituitary gland. In healthy individuals, administration of dexamethasone leads to a measurable reduction in plasma cortisol levels the following day. When cortisol suppression fails to occur, it is interpreted as evidence of HPA axis hyperactivity.
Another assessment tool is the corticotropin-releasing factor (CRF) stimulation test. In this test, CRF is administered intravenously, and ACTH and cortisol levels are measured at regular intervals over two to three hours. In healthy individuals, CRF stimulation increases ACTH release, followed by an appropriate rise in cortisol.
In individuals with severe depression, these responses are often altered. Depressed patients tend to exhibit lower ACTH responses despite persistently elevated cortisol levels, suggesting impaired feedback regulation. Research indicates that depressed individuals often have elevated CRF levels, possibly reflecting chronic stress signaling within the HPA axis.
Importantly, studies have shown that when depressive symptoms resolve, associated HPA axis abnormalities—such as adrenal enlargement and excessive CRF secretion—also tend to normalize. These findings support a close association between HPA axis dysregulation and severe depression, while underscoring the dynamic and potentially reversible nature of this stress-response system.
