Relationships between Sleep Quality and Diurnal Variations in Mood in Healthy Subjects

Research to intraday fluctuations of mood in healthy subjects has indicated that diurnal patterns occur in positive mood states such as vigour, happiness and hedonic tone as well as in negative mood states such as fatigue, depression and anxiety (14). Yet, no clear statements can be made about how mood states are related to time of the day, because conflicting findings have been reported about the timing of minimum and maximum intensities of mood and the pattern of variation during the day. Diurnal changes in mood have been hypothesized to be modulated by circadian rhythms of biological variables (5,6), but they may also be determined by current activities and type of environment (4). Furthermore, in clinical studies disturbances of mood have been found to be related to disturbances of sleep (7). Possibly, in healthy subjects sleep also has an influence on mood. In this study we were especially interested in the relationship between subjective sleep quality of a particular night and diurnal variations during the subsequent day. As far as we know no study has investigated the relationship between subjective sleep quality and diurnal variations in mood in healthy subjects in detail. We studied a group of healthy subjects in their natural environment for three consecutive days and nights. Subjective sleep quality was assessed by means of a brief self-rating questionnaire (8), each morning after rising from the bed. In addition, a shortened version of the Profile Of Mood States (POMS; 9) was used to evaluate the mood after awakening and during morning, afternoon and evening. This allowed us to determine the diurnal characteristics of different aspects of mood and to examine, for each individual day, the relationships between subjective sleep quality and mood states during the course of the day.