When we sleep poorly, we may feel less inclined to participate in social activities. Now, researchers have found evidence that being sleep-deprived can not only make us less sociable, but it can also prevent our peers from seeking us out.

Sleep deprivation can contribute to a host of mental and physical problems, including depression, diabetes, and impaired cognitive functioning. Now, research from the University of California (UC), Berkeley has linked sleep deprivation to another effect: social isolation.

According to the study's senior author, Professor Matthew Walker, "We humans are a social species. Yet sleep deprivation can turn us into social lepers." The findings—which appeared in the journal Nature Communications—indicate that, on the one hand, people who have experienced sleep loss are less eager to interact with others. On the other hand, the results also show that people who are sleep-deprived tend to come across as socially unappealing.

Sleep loss fuels self-isolation

The UC Berkeley research team used functional magnetic resonance imaging (MRI) brain scans, as well as standardized assessments of a person's state of loneliness and innovative tests to see if sleep deprivation was linked to social withdrawal. The researchers recruited a cohort of 18 healthy adults, which they split into two groups. They instructed participants in one group to get a regular night's sleep, while those in the other group had to stay awake through the night.

At the first stage of the study, the scientists monitored the participants' brain activity as they watched short videos depicting individuals with a neutral expression walking toward the viewer. The participants had the option to stop the video when they felt that the person on-screen was getting too close. This allowed the investigators to gauge the participants' levels of comfort with social proximity.

First, the researchers observed that sleep-deprived individuals were more likely than their well-rested peers to keep people at a distance, stopping the videos to keep the walker 18%–60% further back than their peers. Then, the brain scans revealed that sleep-deprived people presented heightened activity in a brain circuit called the near space network, which lights up when we think that we perceive a threatening human presence.

However, the same scans showed that sleep-deprived participants had lower levels of activity in the so-called theory of mind network, which normally assesses emotions and intent in the self and others. These two sets of findings put together suggest that sleep loss impairs a person's ability to correctly assess social situations, rendering the individual more likely to withdraw from social contexts.

"It's perhaps no coincidence that the past few decades have seen a marked increase in loneliness and an equally dramatic decrease in sleep duration," says the study's lead author, Eti Ben Simon, PhD, adding, "Without sufficient sleep, we become a social turn-off, and loneliness soon kicks in."

Alienation is contagious

In another part of the study, the researchers assessed how external observers would perceive sleep-deprived individuals. For this purpose, they recruited 1,033 observers through an online crowdsourcing marketplace.

The observers—who remained unaware of the study's goals—first looked at videos showing the sleep-deprived participants discussing a variety of simple topics. Then, they rated the people in the videos based on how lonely they thought they looked and whether they would be interested in interacting with them.

Next, the researchers asked the observers how lonely they themselves felt after watching the sleep-deprived participants. Surprisingly, after having watched 60-second clips, the observers described feeling more isolated, suggesting that loneliness may be contagious.

In the final stage of the study, the investigators asked participants to fill in standardized surveys, assessing their own state of alienation after just 1 night of either good sleep or poor sleep. This test also confirmed that people who missed out on a good night's sleep were more likely to feel lonely and unsociable the next day.

"On a positive note, just 1 night of good sleep makes you feel more outgoing and socially confident, and furthermore, will attract others to you," says Walker. However, he adds that if a person continually sleeps poorly, this may severely affect their social life and emotional health.

"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. That vicious cycle may be a significant contributing factor to the public health crisis that is loneliness."

—Prof. Matthew Walker