Resistance to suppression by dexamethasone of plasma 11-O.H.C.S. levels in severe depressive illness.

Use of the midnight dexamethasone suppression test showed that the plasma 11-hydroxycorticosteroid (11-O.H.C.S.) level did not undergo its normal reduction in 14 out of 27 patients with severe depression. Resistance to dexamethasone suppression correlated with the clinical rating of the severity of depression, while recovery from depression was associated with return of normal responsiveness to dexamethasone. The explanation of these findings is unknown.