Dexamethasone Suppression Test and Subtypes of Depression

To the Editor.—  There is growing support for the use of the DST for diagnostic and treatment planning purposes in severe depressive illness.^1-4 The recent report by Schlesser et al in the Archives lends support to that group's tripartite classification of primary unipolar depression, based on psychiatric history of first-degree relatives. In this and an earlier study^' the Iowa group found that more than three quarters of patients with FPDD failed to show suppression of morning cortisol level after an overnight DST, with only a few percent of those with DSD similarly not showing suppression.We have tried to replicate their finding in a prospective fashion by performing the DST in consecutively admitted unipolar primary depressives who met Feighner⁵ criteria for unipolar primary depression and Research Diagnostic Criteria (RDC)⁶ for endogenous depression. In addition to 8 AM blood samples as obtained in the Iowa protocol,³ we drew samples