Urban legends suggest that full moons throw everything out of whack, from our moods to fertility to romance. Most of those lunar-themed old wives tales aren't true, of course – but a new study finds that full moons actually do screw with your sleep.
Christian Cajochen, a biologist and lead author of the new paper, was sitting outside a pub with some colleagues, gazing at the full moon, when a thought struck him. Does the full moon influence sleep? After some discussion, he realized that data from his past sleep studies might shed (moon) light on whether the lunar cycle impacts sleep.
"It took me more than four years until I decided to publish the results, because I did not believe it myself," Cajochen, a professor and director of the Centre for Chronobiology at the University of Basel in Switzerland, writes in an email.
To learn if a link between sleep and the moon exists, Cajochen looked at results of a study from 2000 to 2003 that examined circadian rhythms and the sleep- wake cycle. The experiment included 17 healthy young volunteers between age 20 and 31 and 16 healthy older subjects between the ages 57 to 74. At the time, the study had nothing to do with lunar cycles and sleep.
During the experiment, which involved two full nights of sleep and a third night that included either sleep deprivation or sleep satiation (in other words, lots of naps), the researchers took EEG readings and blood samples from the participants. An EEG records electrical activity in the brain and can determine how long and how often a person is in deep sleep. Recently, Cajochen compared the EEG and blood test results with the lunar cycle.
And he found that people experienced better sleep during the new moon and worse sleep during a full moon. During the full moon, it takes an average of five minutes longer to fall asleep and people dozed for 20 minutes less. And, their melatonin levels dropped. Melatonin is a hormone that regulates the sleep-wake cycle by causing drowsiness and a dip in body temperature.
"I was also surprised to see, that besides sleep, also evening melatonin levels were affected by lunar phase," he says.
While Cajochen remains unsure about why people don't sleep as well during the full moon, he speculates that sleep worsens because they see more light, meaning they don't sleep as deeply, because light keeps us awake.
Cajochen admits there's little we can do do to combat poor sleep during a full moon if excess daylight is the culprit. But, these findings will help people who believe the full moon leads to their restless nights.
"If somebody thinks he or she is sensitive to the moon effects on sleep, [doctors] should probably account for that," he says.
The study appears in the current issue of Current Biology.