THE DEXAMETHASONE SUPPRESSION TEST IN PATIENTS WITH MOOD DISORDERS

Background: This study was undertaken to (1) determine whether the end ogenous/nonendogenous mood disorder dichotomy is validated by the dexa methasone suppression test (DST); (2) determine whether other subtypin g schemes (unipolar/bipolar, DSM-III melancholic/nonmelancholic, Winok ur's family history subtypes) relate to the DST; (3) evaluate the rela tive contributions of symptom severity, weight loss, and other factors to DST status; and (4) assess the relative sensitivity of various pos t-dexamethasone cortisol determinations in the detection of dexamethas one nonsuppression. Method: 487 consecutive adult inpatients (N = 131) and outpatients (N = 356) with unipolar (N = 422) or bipolar disorder (N = 65) underwent the 1.0-mg DST. Nonsuppression was defined as at l east one post-dexamethasone cortisol measurement > 4.0 mu g/dL. Result s: Nonsuppression occurred in 27% of all patients with major depressio n and 43% of all bipolar depressed phase patients. For outpatients, de xamethasone nonsuppression occurred in 35.2% of subjects with endogeno us (unipolar + bipolar; N = 145) and 9.0% of those with nonendogenous (unipolar only; N = 211) depressions (single 4 p.m. post-dexamethasone cortisol). For inpatients, dexamethasone nonsuppression was found in 61.5% of subjects with endogenous (N = 104) and 18.5% of those with no nendogenous (N = 27) depressions (three post-dexamethasone cortisol de terminations). For the inpatient and outpatient sample together, the D ST had a sensitivity of 46.2% and a specificity of 89.9% in differenti ating endogenous from nonendogenous major depressive episodes. Weight loss, gender, and symptom severity added little to the endogenous/none ndogenous dichotomy. The Research Diagnostic Criteria (RDC) primary/se condary and Winokur and colleagues' family history subtypes for unipol ar depression were not strongly validated by the DST. The 4 p.m. and 1 1 p.m. samples together detected 91.0% of those inpatients with abnorm al three-sample DST results. The 8 a.m. sample alone detected 30% of t hose, the 4 p.m. sample alone detected 67%, and the 11 p.m. sample alo ne detected 62%. Conclusion: The RDC endogenous/nonendogenous dichotom y was validated by the DST.