Know The Facts

Big moon, little sleep?

The moon exerts a powerful influence on our collective imagination, but what about our sleep? Are stories claiming that people sleep badly during a full moon simply old wives’ tales? Is it possible that this familiar face high in the night sky could be affecting our little sleep patterns down on earth? Researchers have been looking into these questions and their findings might surprise you…


The curious tale of the Swiss sleep study

The influence of lunar cycles on human sleep received a lot of attention in the summer of 2013.

Swiss researcher Christian Cajochen and colleagues published a paper in a respected science journal1 that made a surprisingly unscientific-sounding claim: “the distance to the nearest full-moon phase significantly influences human sleep and evening melatonin levels.”

Out of curiosity, Cajochen’s team had analysed data gathered from a separate research project to see whether they could identify any lunar influence on sleep patterns. The moon hadn’t been considered as a possible issue during the original study so there was little chance of a placebo effect. And the participants had slept under tightly-controlled laboratory conditions in windowless rooms, so they couldn’t have seen the moon or been bothered by bright moonlight.

Nevertheless, the results were striking. Study participants took five minutes longer to fall asleep when there was a full moon compared to when there was a new moon. They slept for twenty minutes less. EEGs showed their ‘deep sleep’ brain activity dropped by nearly a third. Their melatonin levels dipped. And they felt the effects too: participants reported feeling less refreshed the day after a full moon.


Could the folklore be true?

Cajochen was astonished. Even though there were similarities with the results of a previous study, he said, "It took me more than four years until I decided to publish the results, because I did not believe it myself. I was really sceptical about the finding, and I would love to see a replication.

One year later, Maren Cordi, Sandra Ackermann and colleagues did exactly that. They replicated the study2 by performing the same analyses on a different group of people. Critically, however, they had access to much more data – sleep recordings from 1,265 people compared to just 33 people in Cajochen’s sample.

Sadly, for those of us who would like to believe in mysterious lunar influences, the results of this study were null: “we did not find any evidence for an influence of lunar class on objective sleep parameters.” In other words, the moon had nothing to do with whether participants slept well or badly.


If not the moon, then what?

Both sets of researchers note the limitations of retrospective data analyses and call for deliberate, tailored studies to answer this specific question. So it may be some time until the question of whether lunar cycles affect sleep quality can be definitively put to bed.

Until then, there are plenty of small but significant things you can do to enjoy better sleep. And, you’ll be relieved to hear, none of them ask you to change your relationship with the phases of the moon.



  1. Cajochen, C. et al. Evidence that the Lunar Cycle Influences Human Sleep. Current Biology, 2013; 23(15):1485–1488
  2. Cordi, M., Ackermann, S. et al. Lunar cycle effects on sleep and the file drawer problem. Current Biology, 2014;24(12):R549–R550


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