Relationships between sleepiness and emotion experience: an experimental investigation of the role of subjective sleepiness in the generation of positive and negative emotions

Abstract

Problems obtaining quality sleep have been shown to be common. For example, according to a recent survey conducted by the National Sleep Foundation (National Sleep Foundation, 2002), 58% of respondents experience symptoms of insomnia a few nights a week or more. Moreover, sleep difficulties can result in daytime sleepiness, which has been shown to negatively affect a broad range of abilities and states, one of which is mood (e.g., Bonnet, 1994).

While the relationship between sleep and mood is well-studied, the relationship between sleepiness and normal mood among healthy individuals experiencing normal sleeping conditions is not well understood by sleep science. Thus, affective researchers tend to substantiate their affective related notions about sleep from studies of non-healthy participants or participants experiencing extreme sleeping conditions.

Recognizing that both sleepiness and emotions play an important role in the daily experiences of humans, the current study investigated the role of subjective sleepiness in the everyday emotion experience of healthy individuals under normal sleeping conditions. It was hypothesized that subjective sleep appraisals would contribute to appraisals of emotion experience independent of an individual's gender, mood, or the personality dimensions of Neuroticism and Extraversion. An experimental design was employed in which emotional arousal was introduced into the context of a participant's current mood through the use of an experimental task. After exposure to either the experimental or control condition of the task, participants were asked to rate their current emotion experience. Participants in each condition were then classified into groups according to level of subjective sleepiness as measured by the Epworth Sleepiness Scale, Visual Analogue Scale of Alertness, and reported number of hours slept each night. Level of sleepiness was found to affect emotion dimensions, Hostility, Anxiety, Depression, and Contentment. Further, sleepiness explained differences in emotional responses that were not explained by gender, personality, or mood. And while results could not be explained by gender differences alone, it was notable that men reacted to task completion with more hostility than did women, and women reported higher levels of contentment than did men after performing the unsolvable task.

The study is important because it represents the first experimental demonstration to date of the effect of sleepiness on emotion experience in a healthy population. It highlights the importance of healthy sleep for a healthy emotional life, as findings suggest that sleepiness reduces an individual's tolerance for frustration and receptivity for positive emotional experiences.

The current study extends the literature on sleepiness and mood in the following ways: (1) In contrast to much of the sleep literature, the distinction between emotion and mood is recognized; (2) the study draws from both sleep science and affective science in a way that has the potential to make a contribution to both; (3) the study recognizes the importance of positive emotions; and (4) the study was conceived with an eye toward practical applications, particularly those most relevant to a therapeutic situation. Results are discussed in the context of their relevance to improving the well-being of psychotherapy clients.