The pull of the moon has long been associated with everything from menstruation to madness. Many ancient civilizations believed that a woman’s fertility synced up with the lunar cycle and were therefore more likely to conceive when it was out in full. This may be why it’s common for fertility goddesses to have some relation to the moon, be it ownership or otherwise.
The word “lunatic” takes its root from the earth’s lone satellite, as it was long a belief that madness was a result of the full moon. This also began in Ancient Rome and persisted in some form or another for nearly 2,000 years. At the turn of the last century, it wasn’t unusual to see psychiatric patients beaten by doctors during full moons to prevent outbreaks of insanity. And let’s not forget about a certain lycanthrope’s fondness for the lunar cycle.
Over the years, the full moon has been linked to heart attacks, seizures and suicides. Most of these claims were subsequently refuted, but it speaks to the moon’s ability to seduce and inspire that researchers could arrive at such hypotheses.
It also speaks to the full moon being really bright and screwing with your sleep. Many of the manias described above could actually be caused by sleep deprivation. Per Live Science:
In the Journal of Affective Disorders in 1999, researchers suggested that before modern lighting, "the moon was a significant source of nocturnal illumination that affected [the] sleep–wake cycle, tending to cause sleep deprivation around the time of full moon." They speculated that "this partial sleep deprivation would have been sufficient to induce mania/hypomania in susceptible bipolar patients and seizures in patients with seizure disorders."
The key word here is speculated. But something about the moon does tug at our sleep cycle.
A better answer came in the form of a small 2013 study conducted by the University of Basel in Switzerland and published in Current Biology. After studying 33 sleeping participants (one group of men and women between 20 and 31, another between 57 and 74) researchers determined that, while the moon cycle wasn’t an initial factor in the study, the same type of sleep pattern occurred in both groups. Looking retroactively at the subjects, researchers declared that, on average, the subjects took five minutes longer to fall asleep and slept for 20 minutes less. They also had less slow-wave sleep and showed reduced levels of melatonin.
Retroactive research is dubious, at best, but this study was among the first to show that something is at work. The big question is, “Why?” Since the subjects were sleeping in a darkened lab, lunar light could not have affected their cycles. And the authors made it clear that gravity has no affect on human bodies (despite many theories, we’re simply too small for that to be a factor). What, then?
Light rules us all. And the research seems to point to that our sleep patterns evolved to follow a particular lunar cycle, so we would be more attuned to day and night (and the sleeping/waking schedule that demands). The circadian speed bump that occurs when the moon is full is still in question, but seems to suggest that we’re all a part of a greater celestial system. That, or we’re all a little bit werewolf.