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

Some research suggests you may struggle to doze off around this lunar phase.

August 16, 2024

illustration of person in the sky with planets and moon

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An admission: I’m one of those people who will entertain most things on the spiritual front. You think Mercury retrograde is ruining your life? I can relate. You had a gut feeling that turned out to be true? Tell me more. I’m obviously down for all sorts of full-moon lore too. And yet, the effect of a full moon on sleep isn’t just supernatural. Research shows that it may interfere with your ability to doze off or get quality shut-eye—whether you’re a sucker for superstition or a show-me-the-science skeptic.

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.

That likely applies even if you can’t see the moon’s light (whether it’s shrouded by clouds or light pollution or just a great blackout curtain). One hypothesis is that our bodies can sense the full moon’s greater gravitational pull, kinda like the oceans—after all, we’re mostly made up of water. But there are a couple limitations to that theory. For starters, “the tidal effect on humans is estimated to be extraordinarily small,” Brandon Peters, MD, a board-certified neurologist, sleep-medicine specialist, and author of The Sleep Apnea Hypothesis, tells SELF. And the gravitational pull of the moon is about the same during a full or new moon, so you’d expect to see similar effects in both phases, Dr. Peters adds.

Perhaps a more likely explanation involves other changes that happen alongside the shift in gravity of a full moon, Dr. de la Iglesia says, like variations in the Earth’s magnetic field, an energetic shield protecting us from solar winds and other space weather. Though experts don’t quite know how, research suggests that certain geomagnetic shifts might affect your cardiovascular system or even alter your melatonin levels, futzing with your sleep.

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.

Otherwise, simply knowing that your sleep might be affected as a full moon arrives can help you be proactive, Dr. de la Iglesia says. That means following all the common advice for good sleep to a T: Be sure to dim your lights as it gets dark out, ditch the screens about two hours before you cozy up in bed, and practice whatever nighttime routine might help you settle down (whether that includes meditating, reading a book, listening to a soothing podcast, or something else). The idea? The more variables you can actively control, the less likely it is that your sleep will be thrown off by the cosmic powers that be.

Keep in mind, too, that any effects of a full moon on your sleep will let up once the lunar phase passes; and it’s possible that getting, say, 20 or 30 minutes less sleep for a few nights around that time of the month won’t impact you too much. Perhaps you just avoid planning important meetings or calls for those days, if this seems to affect you, Dr. Cajochen says.

For other folks, however, even a slight variation in sleep could be significant, particularly those who have a neurological or mental health condition that is heavily intertwined with sleep disruptions, Dr. de la Iglesia says, such as depression or bipolar disorder (the latter of which has also been shown to be influenced by the lunar cycle). So if you notice that you’re dealing with a surge in symptoms alongside sleep struggles around each full moon, that’s a sign to check in with your doctor, who may be able to tweak your treatment or offer a new solution to help regulate your sleep—moon phase notwithstanding.