Sleep duration and mood
It is widely believed that sleep and mood are interrelated and that prolongation of sleep may have beneficial effects on subsequent mood and general well-being. In the present investigation, it is hypothesised that excess sleep is in fact, detrimental to mood and is associated with a 'Wornout Syndrome', characterised by feelings of fatigue and lethargy, that can persist for up to 5 hours. The studies to be presented here compare the differential effects of Sleep Extension and Sleep Restriction on mood in healthy adults. The experimental design required subjects to undergo one night of Sleep Extension [+2h] and, following an interval of one-week, one night of Sleep Reduction [-2h]. The conditions were counterbalanced. Subjective assessments were conducted hourly on mood states and sleepiness using an adapted Profile of Mood States Questionnaire and the Stanford Sleepiness Scale. Actometers were worn throughout the experimental days and nights. In the first study of 10 subjects results indicated that four subjects were adversely affected by oversleep. Study 2 investigated the effects of sleep duration on mood in 20 healthy adults. Personality factors were assessed using Cattell's 16PF Questionnaire. Subjects maintaining regular sleep schedules reported negative effects of oversleep on subsequent mood. Results indicated that certain personality types were predisposed to the 'Wornout Syndrome' following Sleep Extension. In Study 3, thirty-four subjects were selected on the basis of personality type. It was hypothesised that Introverts, Morning types, Emotionally Tenderminded and Low Impulsives would report symptoms characteristic of the 'Wornout Syndrome' following one night of Sleep Extension. This was confirmed by reports of increased fatigue, diminished vigor, and increased confusion following Sleep Extension. Oversleeping produced greater detrimental effects on mood than a comparable reduction in sleep duration. There are many similarities in symptomatology between the 'Wornout Syndrome' and Chronic Fatigue Syndrome (CFS), specifically, intense fatigue and impaired concentration. Interestingly, chronically fatigued patients often complain of sleep disturbance, and spend much of their time resting in bed. It was hypothesised that the 'Wornout Syndrome' may be a confounding factor in the symptomatology of CFS. As a clinical dimension, twelve subjects were investigated polysomnographically [six were CFS patients]. Findings indicated that CFS patients acquired sleep of longer duration than controls. In addition to excess nocturnal sleep, CFS patients were taking daytime naps. EEG data indicated that these individuals obtained twice the normal amount of slow wave sleep. CFS sufferers may be better advised to regulate their sleep habits and reduce their total sleep time to avoid the confounding effects of the 'Wornout Syndrome'.
- Sport, Exercise and Health Sciences