Sleep On It: The Effect of Daytime Napping on Emotional Reactivity

Sleep has been proposed to play a crucial role in emotional processes. However, studies yielded contrasting results regarding the effect of sleep on emotional reactivity. The present study assessed emotional reactivity in response to negative vs. neutral pictures in 46 (F = 33) healthy university students during 3 sessions. Participants rated affective stimuli for valence and arousal at 11:45 PM (Session 1), an equivalent set at 3:30 PM (Session 2) the same day, as well as at 3:30 PM (Session 3) two days later. Session 1 and 2 were either separated by a 90/120-min nap (NAP group, n = 21) or an equivalent period of wakefulness (WAKE group, n = 25). The study examined physiological and subjective measures of emotional reactivity using heart rate deceleration (HRD) and self-reports, respectively. The findings indicated differential temporal patterns of the effects of daytime naps on emotional reactivity. Notably, the most substantial decrease in HRD was observed immediately following a single daytime nap, underscoring the pivotal role of NREM sleep in this process. Conversely, self-report data indicated an emerging effect two days after the experimental manipulation, specifically influenced by REM sleep. However, it is important to note that our data is preliminary, necessitating further exploration to elucidate the precise contributions of different sleep stages to emotional reactivity. This study offers valuable insights into the complex interplay between sleep and emotional reactivity, emphasizing the need for comprehensive research to unravel the nuanced role of distinct sleep stages in shaping our emotional responses.