The dexamethasone suppression test in depressed patients: clinical and biochemical aspects.

Endogenous depression (ED) is regarded as a psychiatric disease with a biological pathogenesis. Consequently patients with ED respond favourably to somatic treatment, whereas for non-endogenously depressed patients drug-treatment would be often inappropriate. Until now, psychopathologists have failed to define precisely the endogenous subtype of depression on clinical features alone. It is well established that a subgroup of depressed patients shows hypersecretion of cortisol and consequently inadequate suppression of cortisol after a test dose of dexamethasone. This dexamethasone suppression test (DST) was introduced as a laboratory marker, specifically identifying endogenously depressed individuals. This survey illustrates the present dispute about the diagnostic confidence and clinical value of the DST in a psychiatric population, and related biochemical aspects. The following conclusions are stated: (a) use of the DST to validate a theory of nosology is premature. (b) Influence of psychoactive drug medication, diet and weight loss have to be established. (c) Preliminary data suggest that abnormal DST results frequently normalize before clinical recovery and abnormal DST results may be observed before a relapse into depression is clinically apparent. From this it was concluded that the DST might be useful as predictor of clinical outcome. (d) From the association of depressive episodes with disinhibited HPA-activity, a causative role of corticotropin and glucocorticoids in the development of psychiatric illness can be hypothesized. Beside some pharmacological data no supportive evidence for this hypothesis is available. (e) Multisteroid analysis after dexamethasone has provided promising results indicating increased sensitivity of the test when based upon cortisol/11-deoxycortisol ratios and disturbed mineralocorticosteroid secretion in endogenously depressed patients.