Does the dexamethasone suppression test have clinical utility in psychiatry?

The dexamethasone suppression test (DST) has had unprecedented evaluation among biologic tests proposed for application to psychiatric patients. Several techniques for test administration have been devised, including the use of 1 mg of dexamethasone at bedtime, two plasma samples for assay of cortisol (ideally in the afternoon and evening of the following day), and a criterion of greater than 5 micrograms/dl to define nonsuppression. The DST has limited power in differentiating major depression from other acute, severe illnesses but may be useful in comparisons of selected patient populations with affective features or history, and may also have value in predicting and monitoring treatment response. Experience with the DST encourages the search for additional simple biologic tests to help evaluate psychiatric patients.