Hypothalamic-pituitary-adrenal axis function in patients with chronic depression

Hypothalamic-pituitary-adrenal (HPA) axis function in patients with chronic depression has previously been shown to be normal when measured using the dexamethasone suppression test (DST). We examined patients with chronic depression using the sensitive dexamethasone/corticotropin releasing hormone (dex/CRH) test and the dexamethasone suppression test (DST) to establish whether HPA axis abnormalities are present in this group. We also compared the sensitivity of the two tests and compared the results with previous studies in depression that have not specifically selected chronic patients.

Twenty-nine patients with the chronic subtype of major depressive disorder and 28 matched controls underwent examination of HPA axis function.

Neither the cortisol response to the DST or the dex/CRH test differed significantly between the patient and control groups. There was a trend in favour of more patients than controls having an abnormal response to the dex/CRH test (P = 0.052). Neither the patients with an abnormally enhanced response, nor the magnitude of response could be predicted by any illness or demographic variable.

The HPA axis is not overtly abnormal in chronic depression. This contrasts with previous findings in acute depression and bipolar disorder and may suggest that the HPA axis abnormalities present in acute depression resolve, but are not accompanied by symptom resolution. Alternatively, a subgroup of depressives with less HPA dysfunction may progress to chronicity. This has implications for treatment and prognosis. The dex/CRH is a more sensitive test of HPA axis function than the DST in patients with chronic depression.