What’s the science?

Humans are social animals, and social belonging is related to positive outcomes like well-being, while social isolation is associated with negative outcomes like depression and a higher risk for cardiovascular disease. Recent studies have linked loneliness to poor quality of sleep, as people who are socially isolated don’t get enough sleep or good quality sleep. However, it is unclear whether the reverse is also true: Can poor sleep quality lead to greater social isolation by making people less willing to interact with others? This week in Nature Communications, Simon and Walker set out to determine if sleep deprivation results in greater social withdrawal and if so, whether this social withdrawal behavior is related to changes in brain network activation.

How did they do it?

Two studies were conducted – one was online and the other took place both online and in-person. The online study took place on the Amazon Mechanical Turk (MTurk; a website on which people can perform tasks), in which 138 participants kept a log of their sleeping patterns for two nights and completed a questionnaire about social behavior and loneliness. In the second study, eighteen participants completed two versions of a social distance task, in which the experimenter and participant take turns walking toward each other. In both cases, participants indicate when the experimenter is uncomfortably close to them. Thus, this task provides a measure of an individual’s willingness to approach someone, and their receptiveness to being approached. Participants completed this task in-person with different experimenters, as well as a computerized version of this task while undergoing a functional magnetic resonance imaging (fMRI) scan. The fMRI scan allowed the authors to observe differences in activity in two brain networks; one associated with prosocial behaviors (‘Theory of Mind network’; ToM) and the other associated with personal space with respect to other people (‘Near Space network’). These participants were also filmed while answering questions about various topics. Video clips of these participants’ answers were then shown to over a thousand online raters on MTurk, who judged the participants in the videos on how lonely they seemed, whether they would interact and collaborate with those participants, and how lonely the participants made the raters feel.

What did they find?

Sleep-deprived participants exhibited greater social distancing behavior compared to when they were well-rested. This trend was further corroborated with findings from the online MTurk study, wherein poorer quality of sleep was associated with increased self-reports of loneliness and social isolation the following day. Sleep-deprived participants also showed greater activation in the Near Space network and decreased activity in the prosocial Theory of Mind network when they were sleep deprived than when they were well-rested. Interestingly, these changes in brain activity were related to their performance on the social distance task, as the increase in social distancing behavior following sleep deprivation was positively correlated with the increased activation of the Near Space network. Thus, when participants were sleep deprived, they showed a reduction in their willingness to approach others and be approached, which was related to activity in the Near Space network, associated with personal space. Sleep deprivation also influenced others’ perception of the participants, as online raters were more likely to judge sleep-deprived participants as being lonely and were less willing to interact with them. In fact, the raters reported feeling more lonely themselves after watching videos of sleep-deprived people.