Failure to Normalize the Dexamethasone Suppression Test: Association with Length of Illness

It is well-documented that a subgroup of patients with major depressive disorder (MDD) have a state-dependent alteration of their hypothalamopituitary-adrenocortical (HPA) axis, most consistently demonstrated by nonsuppression of plasma cortisol following the Dexamethasone Suppression Test (DST) (Carroll et al. 1981). Although the sensitivity and specificity of this test vary considerably, recent studies of the nonsuppressor subgroup indicate that the test might have prognostic importance. Some investigators (Greden et al. 1980, 1983; Albala et al. 1981; Holsboer et al. 1982, 1983) have shown that conversion to a normal DST (suppression) in this subgroup of patients is associated with a favorable clinical response. As part of a longitudinal investigation of monoamine receptor and neuroendocrine regulation in patients with MDD, we examined the DST results pre and post treatment. We report our results in an attempt to characterize those patients who manifest nonsuppression prior to treatment and either