The role of presleep negative emotion in sleep physiology

Although stress is often presumed to cause sleep disturbances the few studies of stressful events on sleep physiology have resulted in various and sometimes contradictory findings. As this research has focused in particular on more basic elements of stress, it should be intriguing to look at the concrete effects of experimentally controlled stress-related emotions on physiological indicators of sleep such as the EEG. The goal is to explain why sleep patterns change or do not so and in which direction changes occur as a response to pre-sleep emotion. The present study is the first to investigate the influence of an emotionally painful experience on sleep physiology and made use of negative feedback after the performance of a cognitive task. Results indicate that such an experience (namely, failing the task) before the onset of sleep is associated not only with an increase in negative affect but also with changes in sleep physiology. Sleep recordings revealed a significant an increase in sleep fragmentation as expressed by decreased sleep efficiency, increased sleep onset latency, wake after sleep onset, total time awake, number of awakenings during the night, number of awakenings from REM and a decreased % of REM sleep, and SWS. In conclusion, the present study demonstrates that painful emotion correlates with enhanced sleep fragmentation with a decrease of REM sleep the night after the event.