It's the moon's fault, isn't it?

As soon as the full moon shines bright and round in the night sky, the complaints start rolling in: sleepless nights everywhere. “No wonder I can’t sleep, the moon is full again!” Poor moon, it really does get blamed for everything when we toss and turn at night. Instead of blaming coffee, stress, or a late-night Netflix binge, we’re quick to say, “It must be the moon.”

But maybe that’s not so far-fetched after all. Several studies, including ones from Swiss researchers, suggest that the moon might actually have something to do with how we sleep.

A team led by chronobiologist Christian Cajochen at the University of Basel had 17 young and 16 older participants spend multiple nights in a sleep lab, without any clue about what phase the moon was in. And sure enough, during full moon nights, the participants slept about 20 minutes less, took five minutes longer to fall asleep, and experienced around 30 percent less deep sleep. Their melatonin levels, the sleep hormone, also dropped to about half. No surprise then that they felt their sleep was worse during those nights.

We’re all familiar with the day-night rhythm, but apparently there’s also a moon rhythm ticking inside us. Over the roughly 29.5-day lunar cycle, our bedtime shifts later, and our total sleep time gets shorter. Researchers think this might be an evolutionary adaptation. Our ancestors may have used the extra moonlight before the full moon to stay active longer, maybe for hunting, social gatherings, or simply storytelling by the fire.

But why even city dwellers, surrounded by artificial light, still seem to respond to the moon remains a mystery. Perhaps gravity plays a role after all, the moon controls the tides. And since we humans are made up of about 60 percent water, maybe our inner tides sway a little more strongly during the full moon.

Whether it’s the light, gravity, or just our imagination, next time you’re lying awake under a full moon, you can tell yourself, “I’m just moon-sensitive.” And honestly, that sounds a lot more poetic than simply saying, “I can’t sleep,” doesn’t it?