The moon may be a harsh mistress, but she also might be to blame for your poor night’s sleep. A study in Current Biology shows for the first time that the moon’s shape can impact people’s sleep. Specifically, a full moon negatively affects sleep duration, deep sleep, how long it takes to fall asleep, and levels of melatonin (a sleep-related hormone).
With a study like this, it’s important to make sure that nothing unduly influences the results, and the Swiss team responsible ensured this in two ways. First, they made sure the subjects represented a wide range of people (they had 17 healthy young volunteers and 16 healthy older volunteers, with men and women in every group) and the laboratory conditions were carefully monitored and controlled for.
Second, they didn’t bring in the whole “lunar” aspect of this sleep study until much later. As the authors write in the paper, “We just thought of it after a drink in a local bar one evening at full moon, years after the study was completed.” (If it hadn’t been for that full moon inspiration, we might still not have any evidence linking lunar phase with human sleep activity!) All the recordkeeping allowed them to go back to the original data, collected from 2000-2003, and see if any of the sleep characteristics they measured had anything to do with the moon’s phase.
Full moon woes
It was a good thing they did. They found that during a full moon, it took participants 5 minutes longer to fall asleep, and overall sleep time fell by 20 minutes. This despite the fact that volunteers in the sleep study had no actual view of the moon.
In addition, sleep was less restful around the full moon. The kind of sleep activity dubbed “non-rapid-eye-movement,” which indicates deep sleep, fell by 30 percent around the full moon, and melatonin levels fell by about half. The participants reported poorer sleep than average during these times.
So while stories of increased crime sprees during full moons — or werewolves changing shape — are nothing but urban legends, we now have a definite link between the full moon and human behavior. Even with all our modern ways to artificially illuminate the night sky, its natural activity still affects us. Scientists have long known about our circadian, or daily, bodily rhythms, but this study helps shed light on the lesser-understood “circalunar” rhythms of our bodies. These phenomena are known to exist, but we know very little about them, in part because a month-long pattern is harder to observe and study than a daily one.
So next time you get a hint of the full moon fever, you know what that means: go to bed early.