The effects of sleep deprivation on the circadian rhythm of plasma cortisol levels in depressive patients.

The circadian rhythm of plasma cortisol levels was studied in 20 endogenous depressive patients who received one-night sleep deprivation therapy and 10 normal controls who were also deprived of sleep together with patients by estimation at four-hourly intervals over 36 hours. The mean values at each sampling time were compared. The result can be summarized as follows: The mean values of depressive patients tended to be higher than those of controls on the day following sleep deprivation. In depressive patients the mean values on the following day were higher compared to those on the preceding day. In the patients who responded well to sleep deprivation therapy, the circadian variation of mean values which was obscure the preceding day showed an evident rhythm the following day. These findings suggest that sleep deprivation may cause a different effect between depressive patients and normal subjects, and that the possible mechanism of the anti-depressive efficacy of sleep deprivation may be to normalize the disturbed rhythm of the physiological function in depressive patients.