A brief nap during an acute stressor improves negative affect.

Overnight sleep can reduce perceived stress, and improve associated cognitive disruptions and negative affect after an acute stressor. Whether a brief nap can also bestow these benefits in a non-sleep-restricted population is currently unknown. In this study that used a between-subjects design, stress was triggered by administering a modified Trier Social Stress Test to two groups of participants (nap [n = 29], wake [n = 41]). All participants were instructed they would give a speech during the study but the topic would be withheld until later, and then completed a math task. After a 40-min break in which participants watched a neutral video or took a nap monitored with electroencephalography, stress was reinforced by presenting the speech topics and giving participants a 10-min preparation period. Next, instead of giving a speech, the study ended and participants were debriefed. Negative affect, perceived stress and working memory were measured at multiple time points before and after the break. Both groups showed lower perceived stress and improved working memory after the break than before, but a nap did not confer additional benefits for perceived stress or working memory beyond taking a break. However, the nap group exhibited lower negative affect after the break than the wake group, and only the nap group showed a reduction in negative affect compared with initial negative affect levels. These results indicate a nap can improve negative emotions accompanying a stressor to a greater extent than taking a break, and suggest that brief naps may be a useful way to improve mood while experiencing an acute stressor.