Subtypes of unipolar depression distinguished by the dexamethasone suppression test.

The dexamethasone suppression test (DST) was administered to 54 primary unipolar depressed patients and 19 non-depressed hospitalized inpatients. Abnormal DST were found in 23 depressed patients (43%) in contrast to 2 (11%) non-depressed patients (P less than 0.05). Within the endogenously depressed group, 69% of patients categorized as familial pure depressive disease (FPDD) in contrast to 13% of depressive spectrum disease (DSD) patients had abnormal DST results (P less than 0.02). The DSD group had significantly fewer abnormal DST results than all other subtypes of unipolar depression (P less than 0.05). The distinction revealed between DSD patients and other endogenously depressed patients may be due to biological factors or due to the heterogeneous nature of the DSD subtype group.