For centuries myths have claimed peculiar occurrences during full moons. The word lunacy stems from this belief.
Many people feel their sleep quality deteriorates during periods when the moon is full. Analysis of a study of 33 volunteers over four years by Christian Cajochen, at the Psychiatric Hospital of the University of Basel in Switzerland, found a 30% reduction in the duration of deep sleep. Along with the subjects sleeping 20 minutes less on full moon nights. Melatonin the sleep hormone we produce during darkness was also reduced and the participants reported sleeping less well.
The researcher Christian Cajochen acknowledges that this is a small sample and shares his surprise at the results.
“I did not believe it myself, I was really sceptical about the finding, and I would love to see a replication.”
More recently the Max Planck Institute of Psychiatry in Munich did not observe any correlation between sleep and the lunar phases when analysing sleep data from 1265 volunteers.
A 2016 study of 5,800 children aged 9 to 11 using accelerometers found that sleep time reduced by just 5 minutes during a full moon. Unlike the Swiss study, this was unable to monitor brain activity and therefore the depth of sleep.
We know that light has a very significant impact on our circadian rhythm. Its only during the last 100 years that we have lived with artificial light. It is entirely plausible that our brains’ hard-wiring is still programmed to take account of the moon’s illumination.
A moonlit night is after all up to 100 times lighter than an overcast night! During winter when the daylight is halved to just 9 hours, any opportunity to work, hunt or travel under moonlight would have been vital to our ancestors’ survival.
Our lives have progressed enormously during the past 100 years but evolution takes millennia and we should remember that our bodies might have some catching up to do.