A lunar-sleep connection in humans may point to an “echo of our evolutionary past,” says Michael Hastings, a research scientist at the University of Cambridge who studies circadian rhythms. “If you were a hunter–gatherer on the African savanna, you may want to be out hunting at the full moon,” he says. Still, the lunar-sleep relationship was a surprise, says Cajochen, adding that future research is needed to strengthen his findings.
“Lunar rhythms are not as evident as circadian rhythms and are thus not easy to document—but they exist,” Cajochen wrote in the Current Biology article. The impacts of the moon are often masked by influences in our environment like artificial light so most people may not sense them, but exactly how—or if—they are connected with circadian rhythms remains an area to be explored, he says. The authors also note that the moon’s effects may vary across the population. So although some individuals could theoretically point to the moon as a potential cause for the dark circles under their eyes, in other individuals sleep may not be lost.
During the study, participants stayed in the sleep laboratory for four nights but the researchers just looked at data on the sleep patterns for a middle night in order to exclude the “weekend effect” on night number one. Participants in the study were required to keep a very regular sleep-wake rhythm for at least a week prior to coming to the sleep lab, but the researchers acknowledge that there may still have been some carryover from exposures to artificial light sources and the environment, which may have somehow influenced the results.
Still, next time you are feeling particularly sluggish, the findings suggest it might be worth an extra look at the calendar. Or that’s what I’ll do if I get caught dozing at the monitor.