It appears there is some truth in the saying that it is harder to get a good night’s sleep when the moon is full. Tests on Swiss volunteers as they spent nights in a sleep lab showed a link between moon phases and sleep patterns: sleep was more disturbed when there was a full moon.

Led by a team from the University of Basel, the researchers report in the July 25th online issue of Current Biology how they found a full moon disrupts sleep quality.

Lead author Professor Christian Cajochen, who is based at the Centre for Chronobiology at the Psychiatric Hospital of the University of Basel, and colleagues analyzed data taken from over 30 healthy volunteers of various ages as they slept in a sleep lab.

As the participants slept, their brain activity, eye movements, and hormone levels in different phases of sleep were measured.

Neither the lab researchers who took the sleep measurements nor the participants were aware that the authors were later going to do an analysis of the sleep data against moon cycles.

It was only after the lab results were produced that it was decided to compare them to moon phases.

Also, the participants could not see the moon from their beds in the sleep lab.

The analysis showed that the participants did not sleep so well when there was a full moon. This was reflected in both subjective measures (where the participants themselves said whether their night’s sleep had been good or not) and the objective measures.

On nights with a full moon:

  • Brain activity associated with deep sleep (during non-rapid eye movement) fell by nearly a third,
  • On average it took the volunteers 5 minutes longer to fall asleep, and their sleep was 20 minutes shorter, and
  • There was a drop in levels of melatonin, a protein that helps regulate sleep and wake cycles.

The authors write:

“This is the first reliable evidence that a lunar rhythm can modulate sleep structure in humans when measured under the highly controlled conditions of a circadian laboratory study protocol without time cues.”

Cajochen suggests the response to moon phase that they observed, which they call the “circalunar rhythm,” could be a relic of ancient times when human behavior was more heavily influenced by the moon.

It would seem that even for some of today’s humans, paying attention to phases of the moon can be a lifesaver. A study published in 2011 suggests you are less likely to end up as a lion’s dinner if you pay close attention to the moon; in southeastern Tanzania, that is.

There is evidence that many organisms, especially those that live in the sea, are influenced by moonlight.

However, this study finds that even without being able to see the moonlight, the body is somehow still responding to the fact it is a full moon.

It remains for other studies now to uncover the biology that explains this influence.

A large study from the Netherlands published earlier this month suggests that a good night’s sleep boosts the benefits of a healthy lifestyle on the heart.