Research presented last year suggested the world was entering a possible "loneliness epidemic." The negative health effects of loneliness and social isolation are now being linked to increasing rates of early death, with one study going as far as finding these factors as influential on mortality as smoking and alcohol consumption. Now a new study from UC Berkeley has investigated the relationship between poor sleep and loneliness, finding people tend to withdraw and avoid social interaction after even a single night's disrupted sleep. The research comprised of a number of different fascinating experiments involving sleep deprivation and fMRI brain imaging.

The core of the study compared the responses of 18 healthy adults, both after a regular sleep and after a sleepless night. Faced with a video showing a person walking towards them, the subjects were asked to push a button when they felt the oncoming person was getting too close. When sleep-deprived, the subjects tended to pause the video when the approaching person was 18 to 60 percent further away, than after a good night's sleep.

The experiment was conducted while the subject's brains were being monitored, and strikingly, the researchers found a sleep-deprived brain displayed increased activity in an area of the brain known to perceive human threats. Reduced activity was also seen in another part of the brain referred to as the "theory of mind" network, which is thought to encourage social interaction.

The study participants were then recorded talking about regular everyday activities, and those videos were shown to over 1,000 neutral observers. The watchers were asked to rate the subjects on how likely they would be to interact with the person, and how lonely they appeared. The intriguing results indeed found that the sleep-deprived subjects were consistently rated as seeming more lonely, and the watchers were less inclined to want to socially interact with them.

The final, and perhaps most compelling, part of the study came when the watchers were asked to self-report their own sense of loneliness after watching the videos. The watchers were blind to the purpose of the questions or the experiment, yet they consistently reported higher rates of personal loneliness after viewing a video of a sleep-deprived subject compared to a well rested subject.

This fascinating result suggests loneliness, to a degree, can be transmitted almost as a kind of social contagion, triggered in a given individual after they confront a person who themselves are lonely.

"The less sleep you get, the less you want to socially interact. In turn, other people perceive you as more socially repulsive, further increasing the grave social-isolation impact of sleep loss," explains Matthew Walker, senior author on the new study. "That vicious cycle may be a significant contributing factor to the public health crisis that is loneliness."

It's not all bad news though. The study did find that feelings of loneliness and sociability can be influenced by a little as a single good night's sleep. "On a positive note, just one night of good sleep makes you feel more outgoing and socially confident, and furthermore, will attract others to you," adds Walker.

The new research was published in the journal Nature Communications.

Source: UC Berkeley