People deprived of sleep for long periods appear less attractive and more unhealthy than those who are well rested, say researchers.
Volunteers were photographed after eight hours sleep and again after being kept awake for 31 hours.
Observers scored the sleep-deprived participants as less healthy and less attractive, the BMJ reports.
The concept of beauty sleep is well known.
But, according to researchers at the Karolinska Institute in Stockholm, it has lacked scientific support.
The team asked untrained observers to rate the faces of 23 young men and women who had been photographed after a normal night's sleep and then after a night of sleep deprivation.
The photographs were standardised so that people were the same distance from the camera, wore no make-up and used the same expression.
NOTE:YOU SHOULD GET ENOUGH SLEEP PEOPLE