Abstract
Diurnal mood variations are one of the core symptoms in depression, and total sleep deprivation (SD) can induce rapid, short-lasting clinical improvement in depressed patients. Here, we investigated if differential sleep pressure conditions impact on subjective mood levels in young women with major depressive disorder (MDD) without sleep disturbances, and in healthy controls. Eight healthy and eight MDD women underwent 40-h SD (high sleep pressure) and 40-h multiple NAP (low sleep pressure) protocols under constant routine conditions during which subjective mood was assessed every 30-min. MDD women rated overall significantly worse mood than controls, with minimal values for both groups during the biological night (ca. 4 a.m.), under high and low sleep pressure conditions. During SD, nighttime mood ratings in MDD women were lower than in controls and partially recovered during the second day of SD, but never attained control levels. The degree of this diurnal time-course in mood under SD correlated positively with sleep quality in MDD women. Our data indicate that MDD women without sleep disturbances did not exhibit a SD-induced antidepressant response, suggesting that the mood enhancement response to sleep deprivation might be related to the co-existence of sleep disturbances, which is an association that remains to be fully established.
Highlights
Total sleep deprivation (SD) has been described as the most rapid non-pharmacological antidepressant currently known [1]
The two-process model of sleep-wake regulation was proposed to explain sleep-wake cycle disturbances in major depression [3]. This model attempts to explain the effects of SD, REM-sleep disinhibition and reduction of slow-wave sleep (SWS) as the result of a deficient sleep homeostatic process that is linked with mood deterioration in depressive patients [3]
None of our participants had sleep disturbances both subjectively and objectively prior to participating to the study. This was guaranteed by excluding any participants with a Pittsburgh Sleep Quality Index (PSQI) cut-off of 10 and above and, most importantly, by having a sleep polysomnography night prior to admission in the in-laboratory setting
Summary
Total sleep deprivation (SD) has been described as the most rapid non-pharmacological antidepressant currently known [1]. The two-process model of sleep-wake regulation was proposed to explain sleep-wake cycle disturbances in major depression [3] This model attempts to explain the effects of SD, REM-sleep disinhibition and reduction of SWS as the result of a deficient sleep homeostatic process that is linked with mood deterioration in depressive patients [3]. MDD women exhibited higher frontal low-frequency (FLA) wake EEG activity (0.5–5.0 Hz) during SD than that of healthy controls, during the biological night [13] Together, these data indicate that young, moderately depressed women without sleep disturbances do not exhibit a deficiency in the sleep homeostatic process S, as predicted by the S-deficiency hypothesis, but may rather live on an elevated level of homeostatic sleep pressure [11,12]. Under low sleep pressure conditions: subjective mood ratings will not differ between MDD and control women during the course of a 40-h multiple NAP protocol, due to a minimal SD-response in both groups, and will undergo a pronounced circadian modulation
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