Can you remember how well you slept during the last full moon? Do you somehow feel different, even when you’re not aware it’s a full moon?
If so, you’re not alone. Despite somewhat limited scientific evidence, millions of people believe that the moon holds an uncanny power over them.
In this article, I’ll be looking at why people feel the moon has such an influence over them, as well as studies that have been done into this worldwide belief.
Then you can make your own decision as to whether or not you think you’ll sleep differently when the next full moon comes around.
Not just superstitious people
Even casual exposure to the emergency services, law enforcement, teaching or social care will involve contact with firm believers in the adverse effects of a full moon.
From hospitals to police stations, the full moon is sometimes blamed for everything from poor sleep patterns to an increase in accident numbers to sudden psychotic episodes.
Some serious, professional, highly trained individuals are certain the moon affects us. In 2011, researchers published an astonishing figure in the World Journal of Surgery:
More than 40% of medical staff is convinced that lunar phases can affect human behavior
The team then looked into medical data to see if there were any notable changes on typically superstitious days, but found none:
Scientific analysis of our data does not support the belief that moon phases, zodiac signs, or Friday 13th influence surgical blood loss and emergency frequency.
So why the difference between what staff think and what research actually shows? Is it that scientific staff have unscientific superstitions, or did the researchers explored the wrong moonlit avenues?
The Transylvania effect
The Transylvania Effect is a term first coined in academic literature in the 1990s. It describes the belief that the lunar cycle can produce both psychologically and physiologically disturbances in people and populations.
The belief that the moon exerts a direct influence on the body and mind can be traced back to pre-Christian times. Pliny the Elder – a Roman author, naturalist, and philosopher – believed that because the full moon caused heavy dew it must also make the brain become “unnaturally moist”.
That was how, he claimed, the moon caused both epilepsy and lunacy. Hippocrates noted that “no physician should be entrusted with the treatment of disease who was ignorant of the science of astronomy”.
And in various languages, the word lunatic has its roots in the moon. For example, the old English word for lunatic was monseoc, which literally means ‘moon sick’.
In the 21st century, we perpetuate lunar myths in our entertainment and our media. From books to films, from memes to light-hearted end of the world news stories, we constantly repeat the tropes of the Moon’s effect on behavior.
The very earliest calendars were based on the cycles of the moon, with the sighting of the new moon indicating a new phase in the year.
Marks on the walls of the prehistoric painted caves at Lascaux in France are believed by Dr. Michael Rappenglueck, of the University of Munich, to be the earliest lunar calendar.
The series of dots and squares painted among the 15,000 year old drawings of bulls, horses and antelopes represent the 29 day lunar cycle.
Most pre-modern calendars were lunisolar, combining the solar year with the lunar year. The Julian calendar abandoned this in favor of a purely solar reckoning. However, the Islamic calendar opted for a purely lunar one.
It should be noted that lunar calendars have always been particularly popular among agricultural societies. This may well be the foundation for our belief that we sleep less during the full moon.
All full moons rise around the time of sunset. But the so-called “harvest moon” and “hunter’s moon”, which occur during the agriculturally busy late summer and autumn in the northern hemisphere behave in a notable way.
They move across the sky in a way that means there’s no long period of darkness between sunset and moonrise for several days around the full moon.
So our belief in restless sleep on full moon nights may stem from a long-held belief that we should be out working under the full moon.
Is there scientific evidence that the full moon influences behavior?
In nature, we can prove lunar rhythms. A good example is the triggering of the spawning of the coral on the Great Barrier Reef around the full moon in December.
With regard to humans, however, there’s limited scientific evidence to match the vast amounts of anecdotal stories and superstitious beliefs.
Research offers hope that the full moon affects sleep
Some interesting evidence comes from a research study in 2013, which was carried out at the University of Basel in Switzerland.
What made it interesting is that neither the participants nor the team in the lab were told what the study was about, because it wasn’t even the aim of the study at the time. The data was actually retrospectively analyzed later, when the researchers had the idea of seeing what data from a previous study might say about the influence of the full moon.
Another useful feature of the study is that the lab was darkened at the time. So not only were the participants unaware they were in some kind of moon + sleep study, but they would not have seen a full moon shining its bright light through a window either.
So the researchers were able to retrospectively analyze the effect of the full moon on the sleep of the 33 unaware volunteers. And on the nights that there was a full moon, they discovered that:
- The volunteers took 5 minutes longer to fall asleep.
- They had 20 minutes less total sleep.
- They spent 30% less time in the deep sleep phase.
The study author, Prof Christian Cajochen, proposed that since the participants probably weren’t aware of the full moon, perhaps we are naturally attuned to the lunar cycle, saying:
The lunar cycle seems to influence human sleep, even when one does not see the Moon and is not aware of the actual moon phase.
Whilst intriguing, the research hasn’t been without criticism. Perhaps most importantly, 33 people is a small sample and subsequent research with more participants has not replicated the results.
Research shows no lunar effect
In 2014, a team of researchers took note of the Basel research and also re-analyzed the data from three large samples in different studies. The results didn’t back up the original research though:
…in a re-analysis of sleep electroencephalography (EEG) data in three large samples, we were unable to replicate their findings.
In 2015, Swiss researchers recorded the sleep of 2125 individuals using polysomnogram at home. Once again, they found no change in people’s sleep based on the moon:
Our large population-based study provides no evidence of a significant effect of lunar phases on human sleep.
And in 2016, a large international study looked at the sleep of 5812 children aged 9 to 11, in 12 countries.
Although they did find that overall sleep time was 1% less on average during full moon, they question how significant that really is, concluding:
In conclusion, sleep duration was 1% shorter at full moon compared to new moon, while activity behaviors were not significantly associated with the lunar cycle in this global sample of children. Whether this seemingly minimal difference is clinically meaningful is questionable.
Research in 2021 offers more hope for believers in the full moon’s effect
In 2021, a team of researchers published the results of a fascinating study they undertook with communities in Argentina and the United States.
The team used wrist actimetry (wrist-worn sleep tracking) to measure the sleep of communities of indigenous Toba/Qom people in Argentina. Some had access to electric light, but others didn’t. They also compared their sleep patterns with people in a highly urbanized setting in the US.
As with many previous studies, they found that access to electric light was correlated with less overall sleep and delayed onset of sleep. Interestingly, they found a modulation of sleep throughout the moon cycle – both in individual communities and the whole population. They found that the peak of sleep onset time and lowest overall sleep occurred in the three to five days before the full moon.
The fact that they found this effect in college students in Seattle will likely confirm many people’s suspicion that the moon must have an effect because they only later realize there had been a full moon. This is a comment many readers have made below, and one that’s hard to ignore if it happens to you personally.
The researchers suggest that perhaps the moon’s gravity has a role to play. Despite admitting that they couldn’t establish causality in their study, I imagine this is an area for future research to explore. Though as they point out, controlling the moon’s gravitational pull so they can compare people with and without that effect would be somewhat impossible!
As you can see, the research jury is still out on just how much of an impact the lunar cycle has on our sleep. While some studies appear to provide tantalizing evidence that the full moon could be partly responsible for the occasional night of less sleep, others failed to find a significant effect.
The latest study in 2021 is fascinating as it explores both the practical and cultural reasons an indigenous population with no access to electric light would choose to be awake for longer on the nights there’s more natural light.
Why would a group of students in the US also experience a change in their sleep though? Is it the moon’s gravity gently tugging at their desire to fall asleep? Is it ancestral knowledge and behavior engrained in our culture, many moons after we first moved into our high-tech homes? Do they just love a good full-moon party in Seattle?
Do you feel that the moon influences how well you sleep? Does the full moon appear to affect your or someone you know’s behavior? Let me know in the comments below.