To the Editor.—
The dexamethasone suppression test (DST) is employed by clinicians as a sensitive and highly specific tool for the diagnosis of melancholic major depression.1 Our unit recently reported that the single-dose oral administration of caffeine produces dose-related and statistically significant increases in the plasma cortisol level.2 Psychiatric patients, particularly depressed patients, have been reported to consume large quantities of caffeine.3,4 For these reasons, we investigated the effects of caffeine on the standard DST.
Subjects and Methods.—
Twenty-two normal volunteers and six depressed patients 23 to 60 years of age gave their informed consent to participate in this study. All of the subjects underwent a physical and clinical laboratory examination and were in good health. Except for two normal volunteers receiving oral contraceptive medications, all subjects were drug-free for a minimum of ten days prior to participation in the study. Normal volunteers were allowed to continue