Here’s evidence that getting your beauty sleep isn’t just a cliche: Sleep loss can make you appear less approachable to people, according to a new study.

Researchers examined how strangers reacted to 25 men and women after only four hours of sleep and after the recommended eight hours. They found that the less sleep a person got, the less inclined strangers were to socialize with the person.

The study volunteers were first asked to sleep eight hours for two consecutive nights. A week later, the participants were asked to get two consecutive nights of bad rest, where they only slept four hours or fewer. The subjects wore sleep monitors to track their rest and were photographed without makeup after each experiment. They were not told what the purpose of the study was or what the photos were measuring.

A group of 122 strangers then observed the photos. The strangers were asked if they would socialize with the person featured in the image. They were also instructed to rate the participants in the images based on attractiveness, sleepiness, trustworthiness and whether or not they looked healthy. 

Unsurprisingly, the study participants got poorer results in their sleepy photos. Not only were strangers more likely to answer that they didn’t want to socialize with a tired participant, the strangers also rated the volunteers lower in attractiveness and they perceived the sleepy participants to be less healthy. (There was no significant change in trustworthiness ratings.)

“These findings suggest that naturalistic sleep loss can be detected in a face and that people are less inclined to interact with a sleep-deprived individual,” the researchers wrote in the study, which was published in the journal Royal Society Open Science.

There are a few minor caveats with this study. The sample size is relatively small, both with the participants and the strangers, so it’s hard to apply these perceptions to an overall population. 

The study also didn’t take certain psychological biases into account. The strangers had no background information about personality, interests or other factors that may play a role in how people perceive others in real life. The outcomes may have been different if the study participant were looking at pictures of loved ones, for example. It also may have been different if the strangers interacted with the person in person, rather than just judging their appearance based on a photo.

Regardless, the study gives some insight into how sleep affects physical attributes. We already know that good rest benefits a lot of internal functions, like the immune system, the mind and the heart. But this research shows that even just a few nights of sleep loss can take a toll on your outer appearance as well.

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