From werewolves and lunacy to the syncing of menstrual cycles, there are many myths around the influence of the Moon on humans. 

It’s mostly a mixture of folklore and urban legends with dubious scientific merit, but new research suggests that the phases of the Moon do affect our sleep cycles. 

In fact, with a “supermoon” full Moon coming next week it’s likely that you’ll go to bed later and sleep less than on average. 

Evidence of so-called circalunar rhythmicity in humans was first detected in 2013.

The study of 33 people revealed that around a full Moon it took them, on average, five minutes extra to fall asleep, they had 20 minutes less sleep, and their periods of deep sleep dropped by 30%.

The new study, led by senior author and neurobiologist Horacio de la Iglesia at the University of Washington, provides more evidence that the increased moonlight around a full Moon does affect sleep patterns. 

This new experiment involved 98 people in Argentina, all of whom were given a wrist-worn Philips Actiwatch Spectrum Plus to track their sleep/wake patterns. To rule-out the effect of light pollution they used participants within the same indigenous Western Toba/Qom community in Formosa (a rural province of northeast Argentina close to Paraguay), but that now live under three very different levels of urbanization: 

  • 40 in a rural setting with no access to electric lighting.
  • 33 in a rural setting with limited access to electric lighting.
  • 25 in an urban setting with easy access to electric lighting.

The study also used data from a control sample of 464 people in Seattle, Washington in the US collected between 2015 and 2018 as part of a separate study. 

What the study detected over the course of a lunar cycle—28 nights—was a similar pattern of sleep among the people regardless of their location and access to electric lighting. 

It also revealed that it was during the three to five nights before the night of full moon peak that it took participants longer to get to sleep and that they slept for the least amount of time during this period. 

“Our results show that sleep timing is synchronized with the Moon’s cycle under a range of living environments,” reads the paper. “Toba/Qom participants slept less and stayed up later on the days previous to full moon nights, when moonlight is available during the early night.”

That makes sense in a rural area with no access to electricity; the waxing gibbous Moon is “up” already at dusk in the few days before full Moon

The researchers found that the Moon’s effect on sleep appears to be stronger the more limited the access to electric light is. And the greater the access to electric light, the shorter the step and the greater the time it took for people to get to sleep.

However, despite these differences the researchers found the same patterns for those in all three locales—and also among the college students in Seattle. “These results strongly suggest that human sleep is synchronized with lunar phases regardless of ethnic and sociocultural background, and of the level of urbanization,” concludes the paper. 

A lunar rhythm to our sleep? Evidence for the modulation of sleep timing by lunar phases is controversial, and this study was small. But we know the lunar cycle has an influence on many organisms.

During full Moons in October, November and December in Australia’s Great Barrier Reef the corals simultaneously spawn, while the timing and speed of the Christmas Island crabs’ annual migration depends on the phase of the Moon. Perhaps most impressively of all, the patterns of zooplankton moving from the depths of the Arctic Ocean to the shallows—which has been called the greatest animal migration on Earth—appears to work on lunar hours, not solar, and be driven by moonlight

Does biology have a secret Moon clock? Do we? That’s not yet clear, but either way your sleep patterns may be affected over the next few nights in the build-up to Monday’s “supermoon.”  

Wishing you clear skies and wide eyes.