Introduction: Hypothalamic-pituitary-adrenal (HPA) axis dysregulation has been linked with major depression, particularly psychotic major depression (PMD), with mineralocorticoid receptors (MRs) playing a role in HPA-axis regulation and the pathophysiology of depression. Herein we hypothesize that the MR agonist fludrocortisone differentially inhibits the HPA axis of psychotic major depression subjects (PMDs), non-psychotic major depression subjects (NPMDs), and healthy control subjects (HCs).
Methods: Fourteen PMDs, 16 NPMDs, and 19 HCs were admitted to the Stanford University Hospital General Clinical Research Center. Serum cortisol levels were sampled at baseline and every hour from 18:00 to 23:00h, when greatest MR activity is expected, on two consecutive nights. On the second afternoon at 16:00h all subjects were given 0.5mg fludrocortisone. Mean cortisol levels pre- and post-fludrocortisone and percent change in cortisol levels were computed.
Results: There were no significant group differences for cortisol at baseline: F(2,47)=.19, p=.83. There were significant group differences for post-fludrocortisone cortisol: F(2,47)=5.13, p=.01, which were significantly higher in PMDs compared to HCs (p=.007), but not compared to NPMDs (p=.18). There were no differences between NPMD's and HC's (p=.61). Also, PMDs had a lower percent change from baseline in cortisol levels at 2200h than NPMDs (p=.01) or HCs (p=.009).
Conclusions: Individuals with psychotic major depression compared to healthy control subjects have diminished feedback inhibition of the hypothalamic-pituitary-adrenal (HPA) axis in response to the mineralocorticoid receptor agonist fludrocortisone. To our knowledge, this is the first study to examine HPA axis response to MR stimulation in major depression (with and without psychosis), and only the third study to demonstrate that exogenously administered fludrocortisone can down-regulate the HPA axis in humans.
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