NASA says supermoons sometime only happen once a year, but this summer we’ve already had two—and there's a third on the way, coming September 9.

The Instagram-worthy lunar event occurs when the monthly full moon coincides with the point in the moon’s orbit where it’s closest to Earth—meaning it looks bigger and brighter than usual. The best time to watch it is after the sunset in your area when the moon starts to rise.

You might wonder: do full moons actually make people go crazy? (Lunatic does come from the latin luna, or moon, after all.) Research has mostly debunked that theory, but here are four other weird ways the full moon might affect us.

It may regulate your menstrual cycle
The menstrual cycle in reproductive-age women lasts about 28 days, which is similar to the length of a lunar phase (29 days and change). But they may be more closely tied: A 2011 study in the journal Acta Obstetricia et Gynecologica Scandinavica tracked the menstrual cycles of 826 women aged 16 to 25 years. Nearly 30 percent of the women had their period around the full moon. The next biggest grouping of women menstruating during a certain phase of the moon was just 12.5 percent of the participants.

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It could lead to an uptick in births
This one’s tricky: only the supermoon could possibly have this effect, not the fact that it’s a full moon. Researchers tracked 1,000 births in a private hospital in Kyoto, Japan, where the mothers hadn’t been induced. They found that more babies were born the closer the moon was to the Earth, when the gravitational pull is the strongest. However, a full moon—which is unrelated to gravitational pull—had no obvious effect.

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It might mess with your sleep
For a study in the journal Current Biology, participants spent three and a half days in a sleep lab where they couldn’t see clocks or outside light. They were allowed to fall asleep and wake up as they normally would. The Swiss researchers collected sleep data from 33 people and compared it to the phases of the moon. They found that in the four days before and after a full moon, participants took 5 minutes longer to fall asleep, slept 20 minutes less overall, and had 30 percent less deep sleep. They also had lower levels of the sleep-inducing hormone melatonin. This is one of the first studies to establish a link between sleep and our circalunar clock, and the researchers now want to track 30 days’ worth of sleep in individuals. But other research on the subject is mixed and couldn’t replicate past results.

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It may affect surgery outcomes
Researchers found that patients who had an emergency heart surgery called acute aortic dissection repair during a full moon had shorter hospital stays and were less likely to die than patients who had the same operation during two other moon phases. According to a 2013 study in the journal Interactive Cardiovascular and Thoracic Surgery, patients who had their surgery during a full moon stayed in hospital for 10 days, 4 days shorter than people who had their surgery during other lunar cycles. But unfortunately, you can’t schedule emergency heart surgery.