Why a Full Moon Might Mess With Your Sleep, According to Science

This article from Self.com is an illuminating take on the effects of the full moon on sleep. Here is an excerpt:

One of the first studies to draw the full moon–sleep connection was a retrospective analysis published in 2013. Meaning, the scientists didn’t set out to study the moon, but decided to comb through existing sleep data and look for relationships with the lunar phases. The results were a surprise, according to lead study author Christian Cajochen, PhD, head of the Centre for Chronobiology at the University of Basel in Switzerland: Around the full moon, people took five minutes longer to fall asleep, had 30% less deep sleep, and slept 20 minutes less overall. Another small retrospective study published in 2014 mirrored those findings: Participants got, on average, 25 minutes less sleep when the moon was full.

You might think that a full moon could interfere with your rest because it’s the brightest phase—and it’s true that exposure to light and sleep don’t mix. But we all have access to plenty of artificial light before bed these days. What’s more, the people in the studies above were in sleep labs, without much access to the outside world (“Kind of a bunker or basement,” Dr. Cajochen tells SELF of his study). In a 2021 study, to better understand the sleep-moon connection in real-life settings, researchers analyzed sleep markers in people who had varying levels of access to electricity. Unexpectedly, they found a similar pattern across all the groups: Remote communities in Argentina and students in Seattle all went to bed later and got less sleep around full moons (in this case, mostly in the days just prior).

Of course, not all research on the topic confirms that a full moon equals worse sleep; certain studies haven’t found significant evidence of a connection. But the potential role of the moon in the scenarios above still begs the question of how this celestial body might steal your snooze. Here’s why experts think a full moon could impact your sleep and what to do if you find yourself restless during this lunar phase (beyond cursing the cosmos).

Why might a full moon mess with your sleep?

While it’s unlikely that the light of a full moon alone would keep you awake or reduce your sleep quality today, it might have led our ancestors (who lacked artificial light) to stay up later—and perhaps that tendency became ingrained in us, lead author of the 2021 study Horacio de la Iglesia, PhD, a professor in the department of biology at the University of Washington, tells SELF. As noted above, this study found that people usually had the shortest amount of sleep on the nights just before a full moon—which is also when moonlight is most visible in the early evening.

“What we think is that when our ancestors were hunting and gathering, it was highly adaptive to extend the end of the day,” Dr. de la Iglesia says. The extra light of a nearly full moon at dusk would grant them more time to find food before darkness fell—so, as Dr. de la Iglesia posits, why wouldn’t they evolve to stay up later on those nights? Even though we may not be as reliant on natural light now, he notes that our bodies may still be primed, evolutionarily speaking, to delay sleep before a full moon.

It’s also possible that, over time, a bunch of biological and evolutionary ties to the moon have led us to develop a circalunar rhythm—similar to a circadian rhythm, but oriented around the roughly month-long moon cycle, versus a single day. So just like you get sleepy at night and feel more awake as the morning progresses thanks to your internal 24-hour clock, experts theorize that your body might also become more active at night (or less naturally prone to sleep) around a full moon as compared to other phases throughout the month, Dr. Cajochen says.

What to do if you struggle to sleep well around a full moon

The moon’s going to keep moon-ing, but that doesn’t mean you’re doomed to restless nights whenever it’s approaching full status. If you find yourself getting in bed only to toss and turn for a while on those days, Dr. Peters actually suggests delaying your bedtime temporarily by, say, 30 or 45 minutes (while keeping your wakeup time consistent). “By reducing your overall time in bed, you’ll build a stronger sleep drive, which will help you fall asleep more easily,” he says. Also, aim to get 15 to 30 minutes of sunlight after waking up each day, he adds, to keep your circadian rhythm bopping along as usual.