Prediction of clinical course by dexamethasone suppression test (DST) response in depressed patients - physiological and clinical construct validity of the DST.

The present survey highlights the rationale for the use of state-dependent biological markers as predictors of clinical course in depression. Cortisol plasma levels after dexamethasone provide such a tool to monitor clinical progress. Since dexamethasone-resistant cortisol gradually returns to normalcy before a complete clinical remission is seen this measure has a possible predictive potential. Moreover, reversion to abnormal dexamethasone responses is prognostically infaust. Though the dexamethasone test has some merits, technical factors (e.g. exclusion criteria, dexamethasone-kinetics) which invalidate test results deserve careful consideration in future studies. Cortisol hypersecretion is considered as a physiological readout of a central disinhibition. This hypothesis is tested applying corticotropin-releasing factor and corticotropin in normal and abnormal DST responders. The data support the validity of the concept which assumes an intact but overactive pituitary-adrenal axis in a depressed subpopulation. A thesis is submitted which places the variety of biological disturbances in depression between two extreme viewpoints. One view considers all biological disturbances as sequelae to one particular dysfunction, e.g. disinhibition of corticosteroid secretion. The opposite view considers the myriad of biological disturbances as a sign of general loss of order, i.e. increased entropy, the precipitating mechanism of which is unknown.