The relationship between tiredness prior to sleep deprivation and the antidepressant response to sleep deprivation in depression.

Recently it was hypothesized that the antidepressant response to total sleep deprivation (SD) results from a disinhibition process induced by the increase of tiredness in the course of SD. In the present study, the role of tiredness in the antidepressant response to SD is further investigated. Seventy-two depressed patients scored subjective tiredness and depressed mood three times daily (in the morning, afternoon, and evening) on the days preceding and following SD. It was found that averaged tiredness on the day prior to SD was related to the SD response, when the severity of depression prior to SD had been held statistically constant. Also, when both severity of depression and diurnal variation of mood prior to SD were partialed out, tiredness showed a positive correlation with the SD response: patients who reported a relatively low degree of tiredness on the day preceding SD improved by SD. This result suggests that tiredness has an influence on SD effects, and that this influence is independent from that of the severity of depression. The findings are in accordance with current ideas on the role of tiredness as a mediating factor in the induction of the therapeutic effects of SD.