Never mind the pallid face, wrinkles and bloodshot eyes. Missing out on sleep can harm your social life as well as your looks, researchers say.

Psychologists found that people who had too little sleep were not only regarded as less attractive and in poorer health than when they had rested, they were also considered less appealing to socialise with.



The haggard, pasty looks of the sleep-deprived may encourage others to steer clear, just as humans learned over millennia to keep away from their sickly associates on the savannah to avoid picking up diseases.



But looking rough is not enough to put people off, the scientists found. “If someone looks less healthy, you are more likely to withdraw from them,” said Tina Sundelin at the Karolinska Institute in Stockholm. “However, that does not explain the entire effect of not wanting to socialise with them. It’s one of the factors, but it’s not the whole story.”



Mountains of research have thrown up a host of good reasons to avoid the sleep deprived. A serious lack of sleep can make people less optimistic and less sociable, and dent their empathy towards others. People become worse at understanding and expressing emotions and more prone to having accidents. Sleep loss has also been shown to make people more irritable. As Sundelin puts it: “If you can see someone hasn’t slept, you’ll have a good idea that they might not be the best person to be around.”



At first glance, keeping people at arm’s length when they’ve had too little sleep might seem like adding insult to injury. But as the researchers point out, being left alone might be precisely what the sleep-deprived person craves in order to recover.

Writing in the Royal Society journal Open Science, Sundelin and her colleagues describe how they photographed 25 people after two nights of normal sleep and after two nights of only four hours sleep. They then asked 122 others to rate the photos for attractiveness, health, sleepiness and trustworthiness.



A couple of nights of insufficient sleep had no effect on how trustworthy people looked, but raters said they were less inclined to socialise with the sleep deprived, and considered them to be less attractive, less healthy and, of course, more sleepy.



The effects of sleep loss on social appeal were minor though. Having four hours sleep for two nights on the trot led to a mere 4% drop in social appeal, according to the study. More important was how tired people looked, rather than the amount of sleep they actually got. The raters were 20-30% less keen on socialising with people who looked very tired compared with those who looked very alert. “If you want to go out and have a good time, it might not be much fun if the person looks really sleepy,” said John Axelsson, who led the research team.



The study builds on previous work from Axelsson and his colleagues at the Karolinska Institute. In one study, the team reported telltale signs of sleep loss in a group of people who stayed awake for 31 hours after only five hours of sleep the night before. They found a long list of facial clues, from hanging eyelids, redder eyes and dark rings under the eyes, to paler skin, more wrinkles and droopier corners of the mouth.

“Sleep loss has an impact on how other people judge you, so prioritising sleep is not a bad idea,” said Axelsson. “But one shouldn’t be too concerned. The effects are not large. It’s not that no-one wants to be with you when you’ve had too little sleep.”