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does full moon affect sleep - image of lunar phases

Here’s Why You Can’t Sleep During a Full Moon

As a fan of Twilight, I’m well aware that a full moon will wreak havoc on werewolves. But what about us mere mortals? It turns out we’re subject to moon-related issues too. A study published in the journal Current Biology suggests our sleep is significantly impacted by the moon’s 29.5-day lunar cycle. Here’s what you need to know about the connection between a full moon and sleep.

Does a full moon affect sleep?

For the Current Biology study, Swiss researchers had 33 healthy volunteers spend three and a half days at a lab over the course of three years. Seventeen of the participants were between the ages of 20 and 31, and 16 were between the ages of 57 and 74.

During their time in the lab, the researchers measured sleep latency (how long it takes to fall asleep), overall sleep time, time spent in REM sleep and deep sleep, brain activity during deep sleep, and nighttime melatonin levels.

The study authors originally intended to examine the internal biological rhythm that controls our sleep/wake cycle—but while grabbing drinks at a bar with a full moon in the night sky, they wondered whether they could extrapolate any data about the potential influence of lunar phases on sleep.

When they analyzed the data, they found:

  • Sleep latency increased the closer it was to a full moon. On nights when there was a full moon, it took about five minutes longer for the volunteers to fall asleep. Once the full moon passed, it became easier for volunteers to fall asleep.
  • Volunteers got about 20 minutes less sleep overall during a full moon and reported their worst sleep quality in this phase of the lunar cycle.
  • Volunteers also spent 30% less time in deep sleep, the most restorative stage of sleep, during a full moon. EEG scans showed they also had reduced brain activity in deep sleep during a full moon.
  • Nighttime melatonin levels dropped leading up to a full moon and were at their lowest on full moon nights.

Why you can’t sleep during a full moon

It’s unclear why there’s such a correlation between a full moon and poor sleep, but scientists do have some ideas. “Researchers suggest that we may carry within us an internal biological rhythm that is linked to the moon’s cycle,” explains sleep psychologist Michael Breus, PhD, in an article for Psychology Today. “Researchers liken this approximately 30-day ‘circalunar rhythm’ to our circadian rhythms, which regulate several biological functions—including sleep—on a 24-hour cycle, in basic alignment with night and day.”

Alon Avidan, MD, neurology professor at the David Geffen School of Medicine at UCLA and director of the UCLA Sleep Disorders Center, tells Elemental that the light from the moon (particularly a full moon) can suppress melatonin production and make insomnia worse. “The light exposure from the moon is essentially sunlight that’s filtered a little bit,” he says. “It can be very physiologically activating.”

Astrologists have a different theory. They believe that the moon controls the ocean and all of the waters on Earth—and because human bodies are made up of 50% to 70% water, the moon has an effect on our moods and sleep.

“[It can be harder to sleep] due to the direct impact the moon has on the water element in our bodies,” Jaya Jaya Myra, spiritual wellness expert, tells Bustle. “The average human body is [mostly] water, making the moon quite capable of altering our mood and mental state. If the mind is turbulent, it is difficult to sleep.”

Regardless of why a full moon messes with your sleep, there are steps you can take to ensure you catch those much-needed Z’s when it’s that time in the lunar cycle. The next time there’s a full moon outside and you can’t seem to drift off, try these tips:

Christina Heiser is the content manager at Saatva. She has held previous positions at Everyday Health, Women's Health, and L'Oréal. When she's not working, you can find Christina checking out the latest boutique fitness classes in New York City, cheering on her college basketball team (go Red Storm!), and trying new beauty and wellness trends.