Full moon shortchanges sleep

Lab experiments show people’s sleep suffers for a day or so every month

wolf moon

People don’t become werewolves during a full moon. But they may lose sleep, a new study shows.


Werewolves aren’t the only creatures thrown off by the moon’s cycles. A full moon subtly disrupts people’s sleep, reports a Swiss team of scientists. Even people dozing in a lab without windows experienced a small shortfall in zzz’s.

Neuroscientist Christian Cajochen from the University of Basel and his coworkers studied data from 33 people. All had volunteered to take part in a sleep study. Because the first night sleeping away from home might prove uncomfortable or novel, the study focused on the participants’ second night of sleep.

If that second night fell close to a full moon, the men and women needed five extra minutes to doze off. They also slept about 20 fewer minutes and less deeply on those nights. The researchers published their findings July 25 in the journal Current Biology.

These new data suggest the moon’s cycles can subtly affect sleep cycles. These internal cycles may be similar to the roughly 24-hour circadian rhythms driven by the body’s internal “clock.” One big difference: The body’s clock is set by sunlight.

Cajochen wasn’t sure he wanted to publish the new findings. Folk tales are more likely to connect the moon’s cycles to human behavior than serious scientific studies are. “If you publish lunar stuff, you are going to be put in the ‘lunatic’ corner and not be considered a serious sleep researcher anymore,” he told Science News.

Yet other scientists say Cajochen and his team performed sound science. This study is the first to find that the moon influences human sleep, says Kenneth Wright. A sleep researcher at the University of Colorado at Boulder, he told Science News that the Swiss team used good methods. “This was done under really controlled laboratory conditions.”

The Swiss team doesn’t know how the moon affects sleep. The gravitational attraction of the moon causes ocean tides to rise and fall. But that force is too weak to affect sleep, Cajochen says. He suspects some internal body clock may be tied to the moon cycles. Lunar cycles have been noted in sea animals that keep track of the tides.

There may be another explanation, says David Dinges. This sleep researcher at the University of Pennsylvania in Philadelphia says that the circadian clock is very sensitive to light at night. Volunteers’ sleep could have been altered by exposure to extra moonlight before arriving at the lab.

More studies are needed to figure out why sleep suffers when the moon is full.

“Stay tuned,” Dinges told Science News. “There’s going to be a lot more research to nail this down.”

Power Words

circadian rhythms Biological functions such as body temperature and sleeping/waking times that operate on a roughly 24-hour cycle.

lunar A prefix referring to the moon.

neuroscience Any of the sciences that deal with the structure or function of the nervous system and brain.

ocean tides The alternate rising and falling of the sea, usually twice in each lunar day at a particular place, due to the attraction of the moon and sun.

Stephen Ornes lives in Nashville, Tenn., and his family has two rabbits, six chickens and a cat. He has written for Science News Explores since 2008 on topics including lightning, feral pigs, big bubbles and space junk.

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