The Full Moon Kept You Up? Let’s Check Her Alibi

It’s 3am. You’re awake, staring at the ceiling like it owes you money. You roll over, and there she is through the gap in the curtains: the moon, huge and smug and extremely full.

Well. That explains everything.

Or does it? The full moon has been blamed for bad nights, strange moods and at least one ill-advised text since humans first lay down under her. For once, there’s actual science to look at. Let’s check her alibi.

Exhibit A: the lab that wasn’t looking

In 2013, sleep researchers in Basel dug up data from an old study that had nothing to do with the moon. Thirty-three volunteers had slept in a windowless lab: no clocks, no sky, no idea what the moon was up to. Neither were the scientists.

When they finally lined the nights up against the lunar calendar, things got interesting. Around the full moon, people took about five minutes longer to fall asleep, slept about 20 minutes less, and lost around 30 percent of their deep sleep. Their melatonin, the hormone that whispers “bedtime” to your body, dipped too. And they said they slept worse. From a room where they couldn’t even see her.

Suspicious. But 33 people is a very small jury.

Exhibit B: the big studies shrug

Science did what science does and checked. In 2014, a team at the Max Planck Institute went through 2,097 nights of sleep from 1,265 people and found… nothing much. No meaningful link between sleep and the moon.

They also spilled some tea about their own field. Sleep labs are sitting on more than 20,000 unpublished nights of data, and results that say “the moon did nothing” rarely get written up. It’s called the file drawer problem: the juicy findings get published, and the boring ones get filed away where nobody reads them.

A year later, a Swiss study wired up 2,125 adults sleeping in their own beds. Full moon, new moon, everything in between: same amount of sleep, same stress hormones, same reviews of their own nights. The researchers’ title was a mic drop: bad sleep, don’t blame the moon.

Case closed? Not quite.

Exhibit C: it’s the nights before

In 2021, researchers from the University of Washington and Yale skipped the lab and followed people living their actual lives. They strapped sleep trackers onto 98 people in Toba-Qom communities in Argentina, some with no electricity at all, and 464 college students in Seattle, who have never met a bedtime they respected.

Everyone’s sleep moved with the moon. On the three to five nights before a full moon, people went to bed about 30 minutes later and slept less. Across the lunar month, sleep swung by roughly 46 to 58 minutes. The effect was strongest in the dark countryside, but it showed up under city lights too.

Here’s the twist: not the night of the full moon. The nights before it. That’s when a waxing moon is already bright and rises in the late afternoon or evening, lighting up the first hours of the night. For most of human history, a bright evening was an invitation: keep talking, keep working, stay up a little longer because you could finally see. Some of us, apparently, still RSVP yes.

The same year, a study from Uppsala University recorded one night at home for 852 adults. The men, not the women, slept less soundly and lay awake longer while the moon was growing toward full. The researchers were careful to call it a link, not proof. Still. Gentlemen.

The verdict

The biggest, most careful studies say the full moon isn’t wrecking most people’s sleep. A few good ones find a small nudge: a later bedtime, a bit less sleep, mostly in the days before she’s full, and mostly where nights are properly dark. Why? Moonlight is the lead suspect. Gravity and some ancient inner clock have been named too, but nobody’s been charged.

What’s beyond doubt is that evening light delays melatonin and pushes bedtime later. The moon is dim next to your phone, but if she’s shining straight onto your pillow, she counts.

And one more thing, said with love: we remember the restless night under a full moon, and we conveniently forget the restless night under a crescent. Expecting the moon to keep you up is a great way to lie awake waiting for it. Your bad night is real. The moon may just be taking the blame for your week.

How to sleep anyway

Close the curtains. Blackout curtains or an eye mask. You can’t be kept awake by a moon you can’t see.

Guard the nights before. If you tend to feel wired, it’s the three or four evenings before the full moon that need protecting, not just the big night.

Dim the rest. If the moon is already lighting your evening, you don’t need two more hours of bright screen on top.

Keep your mornings boring. Same wake-up time, even after a late night. Your body will thank you by Thursday.

Don’t wrestle the pillow. If you’ve been awake a long time, get up, go somewhere dim, read something gentle, and come back when you’re drowsy.

Collect your own evidence. For two or three months, write one line every morning: how you slept, and the moon’s phase. Maybe the full moon really is your restless week. Maybe it’s the week before your period. Maybe it’s just Sundays. At least you’ll know who to blame.

A little light, once a month

For thousands of years, the full moon meant light after dark: a night to travel, to gather, to stay up telling stories. Some of that old restlessness might still live in us. So if she keeps you up, you don’t have to take it personally. Close the curtains if you need the sleep. Or, once in a while, go to the window and let her be what she’s always been: the one night a month the dark leaves a light on for you.

When do my restless nights really happen, and what else was going on that week?

What do I stay up for when the evenings are bright?

What would help me rest on the nights I can see coming?

The research behind this piece: Cajochen et al., Current Biology, 2013 · Cordi et al., Current Biology, 2014 · Haba-Rubio et al., Sleep Medicine, 2015 · Casiraghi et al., Science Advances, 2021 · Uppsala University, Science of the Total Environment, 2021

Feya is for reflection, not medical advice. If poor sleep is lasting or affecting your days, it’s worth talking to a doctor.

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