Specificity of the salivary cortisol dexamethasone suppression test across psychiatric diagnoses

One hundred forty-eight psychiatric inpatients, 12 outpatients, and 17 normal controls were given the 1.0-mg overnight Dexamethasone Suppression Test (DST), with salivary cortisol concentrations being measured as the dependent variable. Based on the Structured Clinical Interview for DSM-III, the patients were diagnosed as having major depression with melancholia (n = 21), nonmelancholic major depression (n = 50), mania (n = 15), schizophrenia (n = 32), dementia (n = 6), substance dependence/abuse n = 18), and miscellaneous (n = 18). Neither the melancholic major depressives nor the entire group of major depressives had significantly higher salivary cortisol pre- or postdexamethasone as compared with all the other patients combined, nor did the melancholic patients have significantly higher cortisol than the nonmelancholic depressives. The inpatients as a group had significantly higher pre- and postdexamethasone cortisol values than the normal controls; cortisol values for the outpatients were intermediate between these two groups. Illness severity (in the depressives), length of time in hospital before the DST, and medication regimen were all unrelated to DST outcome. Thus, in this study, the salivary cortisol DST showed little clinical utility in discriminating major depressives with and without melancholia from other patients with a broad range of psychiatric diagnoses. The test did distinguish between hospitalized psychiatric patients and normal control subjects and between depressed inpatients and depressed outpatients, indicating that hospitalization-related variables contributed to DST outcome.