Those who do not sleep well are less interested in interacting with others, according to sleep researcher Dr. Christian Benedict. He explains why this could be problematic and what effects too little sleep has.

Those who have not slept well are less productive and their cognitive abilities are limited. But lack of sleep could also have a negative impact on social interaction, as an experiment by Uppsala University in Sweden shows. The study was published in the journal “Nature and Science of Sleep”.

In the study, 45 young subjects were shown pictures of different facial expressions. Once when they had slept eight hours and once when they had not slept at all. The eye movement of the subjects was measured with a sensor technology. In addition, respondents had to indicate how they rate the fearful, angry, neutral, and happy facial expressions in terms of attractiveness, health, and trustworthiness. Since the study has a very small number of subjects, the significance of the results is limited. By examining the young, healthy participants, the researchers do not know whether these findings also apply to older people or people who suffer from chronic sleep deprivation.

An experiment on sleep deprivation

In order to carry out such an experiment, it is important that a group that is as homogeneous as possible is examined and that confounding factors are ruled out in advance, explains sleep researcher Dr. Christian Benedict from Uppsala University in Sweden. He is one of the study authors. “For example, we only allowed women to take part in the study who use hormonal contraception. Because a natural menstrual cycle has an influence on sleep and this could have falsified the result of the experiment.” The small study size of a little less than 50 subjects comes about because the research has to remain affordable and feasible.

The subjects had a moment to look at the pictures of the happy, neutral, angry, and fearful expressions. “The images were therefore not shown directly one after the other in order to minimize mutual interference. In addition, half of the subjects were shown the images first when they were well rested and the other half first after sleep deprivation,” explains the sleep researcher on the methodology.

Too little sleep and no desire for social interaction

One result: Aggressive, neutral and anxious facial expressions are classified as less trustworthy by people who have not had enough sleep. “I find it a bit problematic that the anxious facial expressions seem less trustworthy and less socially appealing to the sleep deprived. It means I’m less empathetic.” Actually, as social beings, people should try to help an anxious person and maybe even take away their fears, says the sleep researcher. However, the study suggests that sleep-deprived people tend to stay away from anxious people. Another result: “Anyone who has slept too little does not recognize the nuances in social communication well. The reason: sleep-deprived people have a delayed reaction.”

The aim of research is always to integrate the results into a larger context, describes Christian Benedict. A previous study from California showed people video of unknown people walking towards them in a magnetic camera that measures brain waves. The subjects also had the option to stop the video. The result: In the sleep-deprived, brain regions that warn us about threats were more active when they watched the video of the unknown person. “I’m very tired, I’m not at my best. I’m averse to social contacts and don’t want to interact with other people,” summarizes Christian Benedict.

Long-term lack of sleep could promote loneliness

A study by Solna University’s Karonlinska Institute suggests that sleep deprived people are less attractive to others. Means: “On the one hand, we rate sleep deprived people as less attractive and on the other hand, other people who have an aggressive, fearful or neutral facial expression appear less trustworthy if we ourselves have not slept enough. This could have a negative impact on affect social interaction and our desire to interact socially,” says Christian Benedict. “We’ve all experienced what it means to be disconnected during the pandemic. So in the long run, lack of sleep could make us more lonely. It’s not healthy. We need social contact.”

Lack of sleep can also have a negative impact on relationships and social interaction in other ways: “We are more impulsive, aggressive and easily irritable. For example, we cannot be a good partner with sleep deprivation. We probably do not go with our pubescent children either confidently,” says Christian Benedict.

Sources: Nature and Science of Sleep study, Karolinska Institute study in BMJ, California study in Nature Communications