Cortisol suppression index: a new approach to interpreting the DST in depression.

The cortisol suppression index (CSI) is a ratio of pre- to postdexamethasone plasma cortisol concentrations. In a sample of 24 psychiatric inpatients, an 8 a.m. CSI detected 66% of patients with major depression. Further studies with larger samples and additional controls, including normal subjects, are suggested to validate these prospective findings. This index may serve as a useful and more practical way of detecting major depression in outpatients.