A full moon is sometimes blamed for a bad night sleep, but evidence of a link between the two common events has been lacking. A small study appears to have found some evidence there may be some truth to the myth.
Swiss researchers at the University of Basel have found people sleep worse when the moon is full, regardless of if they can even see the brighter celestial body in the sky.
"The lunar cycle seems to influence human sleep, even when one does not 'see' the moon and is not aware of the actual moon phase," study author Dr. Christian Cajochen, researcher at the Psychiatric Hospital of the University of Basel, said in a news release.
The data gathered for the study, published July 25 in Current Biology, originally was just to measure subjects' sleep patterns based on age and gender between 2000 and 2003. Cajochen's team enlisted 33 volunteers and split them into two age groups, younger adults and older adults. They were sent to a sleep lab at the hospital where their vital signs, brain waves, eye movements and hormone levels were monitored by scientists.
But, TIME senior editor Jeffrey Kluger told CBS This Morning that the researchers were sitting in a bar a decade later when it was a full moon, and wondered aloud what it would look like if they went back to the study and measured the data against the lunar calendar.
The researchers discovered that during a full moon, participants took on average five minutes longer to fall asleep. They also got 20 fewer minutes of sleep overall compared to their sleep when the moon wasn't full. Brain activity indicative of deep sleep dropped by 30 percent during the full moon.
The subjects had measurably lower levels of melatonin, a hormone known to regulate the sleep and wake cycles. The participants also reported their sleep was poorer when the moon was full, despite not being able to see the moon whatsoever from their rooms.
The researchers called the study the first reliable evidence that a lunar rhythm can alter sleep structure in humans even when measured in a highly-controlled lab setting.
"I was very skeptical until we saw the data," Cajochen told Bloomberg.
He and his colleagues speculate this link may date back to ancient times, when human and animal behavior, such as for reproductive purposes, were synchronized by the moon. Electrical lighting may stunt this effect.
They concluded despite the comforts brought by modern civilization, the timeless geophysical rhythms of the moon still affect us. But, the moon may not be all that bad -- the researchers said it could turn out that the moon has power over other more positive aspects of our behavior, such as potential boosts in mood or cognitive performance.
"What's nicest about this study is that it uses data that wasn't originally intended for this purpose, so you know there couldn't be any bias and that makes it quite convincing," neuroscientist Kristin Tessmar-Raible, a researcher at the Max F. Perutz Laboratories in Vienna who was not involved in the new study, told Science. "And the question now is what is the mechanism behind this?"