Given the known detrimental effects of poor sleep on an array of psychological and physical health processes, it is critical to understand the factors that protect sleep, especially during times of stress when sleep particularly suffers. Positive affect (PA) arises as a variable of interest given its known associations with health and health behaviors and its ability to buffer stress. In 2 studies, we examined which types of PA (distinguished by arousal level and trait/state measurement) were most beneficial for sleep and whether these associations varied depending on the stress context. In Study 1, college students (N = 99) reported on their PA and sleep during the week of a major exam. In Study 2, 2 weeks of daily PA and sleep data were collected during a period with no examinations in a similar sample of students (N = 83). Results indicated that high trait vigor was tied to better sleep efficiency and quality, especially during high stress. Trait calm was generally unhelpful to sleep, and was related negatively to sleep duration. State calm, on the other hand, interacted with stress in Study 2 to predict more efficient day-to-day sleep on days with higher average stress. These findings illustrate the importance of considering arousal level, affect duration, and the stress context in studies of PA and health. (PsycINFO Database Record

Smiling has been previously shown to improve stress responses. We replicated and expanded this work by testing whether smiling helps with a potent real-world stressor: a vaccination-like needle injection. We also extended past research by examining grimacing, a facial expression known to naturally occur during stress and pain and one that shares some of the same facial action units as smiling. Participants (n = 231; [M]age = 19.2) were randomized to hold either a Duchenne smile, a non-Duchenne smile, a grimace, or a neutral expression while receiving a 25-gauge needle injection of saline solution. Expression was covertly manipulated via cover story and chopstick placement in the mouth. Heart rate (HR) and electrodermal activity (EDA) were collected continuously alongside self-reports of pain, emotion, and distress. Repeated-measures analysis of variance (ANOVA) indicated a between-subjects effect of facial condition on self-reported pain as well as a Condition × Time effect. Probing each time point revealed the strongest effect to be at needle injection, where the Duchenne smile and grimace groups reported approximately 40% less needle pain versus the neutral group. Repeated-measures ANOVAs also revealed differences between conditions for both HR and EDA. In post hoc analyses, only the Duchenne smile group exhibited significantly lower HR than neutral, with marginal Duchenne benefits found for EDA. Together, these findings indicate that both smiling and grimacing can improve subjective needle pain experiences, but Duchenne smiling may be better suited for blunting the stress-induced physiological responses of the body versus other facial expressions.

The natural process of mimicking the facial expressions of others is well established, as are the deficits in this reflexive behavior for individuals with clinical disorders such as depression. This study examines the extent of this deficit in non-clinical individuals with high transient negative mood, and whether it extends to both automatic and effortful emotion expression behavior. One hundred and thirty-six participants were shown happy, sad, and neutral faces, while electromyography (EMG) recorded facial muscle responses. Automatic (reflexive) mimicry was assessed while participants simply viewed facially expressive photographs, while effortful mimicry was monitored when individuals were told to intentionally copy the expressions in the photographs. Results indicated that high levels of negative mood were primarily associated with deficits in effortful mimicry of happy expressions, although some similar evidence was found in automatic mimicry of happy faces. Surprisingly, there were also ties between negative moods and inaccuracies in effortful mimicry of sad expressions (but not automatic mimicry). Inaccurate automatic and effortful mimicry were also tied with lower self-reported social support and greater loneliness. These results indicate that even in healthy individuals, transient and minor changes in negative mood are tied to deficiencies in facial mimicry at both the automatic and effortful level.