Physiological Sleep Propensity Might Be Unaffected by Significant Variations in Self-Reported Well-Being, Activity, and Mood

Background and Objective. Depressive state is often associated with such physical symptoms as general weakness, fatigue, tiredness, slowness, reduced activity, low energy, and sleepiness. The involvement of the sleep-wake regulating mechanisms has been proposed as one of the plausible explanations of this association. Both physical depressive symptoms and increased physiological sleep propensity can result from disordered and insufficient sleep. In order to avoid the influence of disordered and insufficient sleep, daytime and nighttime sleepiness were tested in winter depression characterized by normal night sleep duration and architecture. Materials and Methods. A total sample consisted of 6 healthy controls and 9 patients suffered from depression in the previous winter season. Sleep latency was determined across 5 daytime and 4 nighttime 20-min attempts to nap in summer as well as in winter before and after a week of 2-hour evening treatment with bright light. Results and Conclusions. Patients self-reported abnormally lowered well-being, activity, and mood only in winter before the treatment. Physiological sleep propensity was neither abnormal nor linked to significant changes in well-being, activity, and mood following the treatment and change in season. It seems unlikely that the mechanisms regulating the sleep-wake cycle contributed to the development of the physical depressive symptoms.