It’s Not Just Folklore: The Impact of the Moon on Sleep
When my middle child was about a year old, he would occasionally break from his usual sleep pattern to wake up in the middle of the night and be wide awake – babbling and smiling, full of energy and ready to start the day.
The pattern lasted for a few days, then he’d return to his regular programming of sleeping through the night. It took a few cycles to realize this pattern happened every month, around the full moon.
This made sense because he had a skylight in his ceiling exposing him to moonlight – we would stand together looking up at the sky, talking about the moon. We promptly ordered a custom blackout shade to ensure no light would seep through.
Problem solved.
Imagine our surprise when, after the shade was installed, he continued his pattern of waking up monthly – the same cheerful, babbling wake-up call at 3 AM – yet now there was no light in his room.
We lived in Portland, Oregon, a notoriously cloudy and rainy place. Looking back to before the shade was installed, he awoke around the full moon, even when there was no visible moonlight. And now there was a shade blocking out the moonlight, yet he was still waking up.
What was going on?
Is There More to the Folklore?
Howling at the moon, lunacy, moonstruck – the impact of the moon on the human psyche is an undeniable piece of folklore, but is there more to it?
There are some research studies that show a link between the full moon and sleep. But frankly, there are also studies that find no connection.
For the sake of confirmation bias and following my own thread of interest, I’m going to tell you about the legitimate research that did find a link.
What The Research Found
The first was in 2013. Subjects reported to a sleep lab over a three-year period for a study on aging and sleep (unrelated to moon cycles). Retrospectively, that same data was analyzed for lunar phase and found the following tendencies around the full moon:
30% measurable drop in deep sleep
5 minutes longer to fall asleep
20 minutes less total sleep time
Lower self-reported sleep quality
Lower melatonin levels upon measurement
In 2021, researchers tracked sleep patterns among Indigenous tribes in Argentina with varying levels of access to electricity. The same study followed university students in Seattle. Across every group, the researchers found subjects fell asleep later (~30 minutes) and had less total sleep (~50 minutes) in the days leading up to a full moon.
The effect was strongest in the communities that had no access to electricity, where the sky was more visible, yet it was still measurable in the college communities with full electricity and plenty of light pollution inside and out.
What might be the cause?
What the researchers concluded is where it gets really interesting…
In the 2013 sleep lab study, the researchers concluded that humans may have an internal rhythm, or internal clock, of approximately 29.5 days connected to the lunar cycle, speculating that this could be a leftover mechanism from more primitive times when behavior could have organized around the moon for reproduction or other purposes.
The subjects were in a windowless lab with no clocks and no idea that lunar cycles were happening and/or would later be studied using the data they were providing.
The researchers of the 2021 study proposed that the lunar sleep changes could be related to melatonin, the hormone released in darkness, which can be suppressed to some degree by moonlight. Yet many of the subjects weren’t exposed to natural darkness, had plenty of artificial light exposure with the same light conditions every day, and still showed sleep changes around the lunar cycle.
So they left the door open to other potential mechanisms. They too floated the possibility of a human cycle, closer to 15 days, to cover both the new moon and full moon cycles.
Perhaps some of these mechanisms explain my baby’s middle-of-the-night wakings even when it was cloudy, even with the shade?
Note: Whether the moon affects men and women differently, and/or connects to other hormonal cycles, is still an open question. How the moon cycle impacts humans in general has the strongest evidence behind it.
What Have You Noticed?
What do you think? Have you experienced sleep changes around the full moon or noticed it in your kids, partner, or even your pets? Any other physiological or mental/emotional changes you notice around the full moon that may or may not be related to sleep?
The next full moon falls on September 26, a few days after the autumn equinox. Pay attention to your sleep in the days leading up to it and see what you notice.
Warmly,
Dr. Krista
Olive Says
Oh come on people…
Have you never heard of werewolves?