The science behind lunar theory
Legend and folklore places a lot of emphasis on the moon. The idea that the moon affects human behavior is as old as those legends (werewolves, anyone?).
While there’s plenty of evidence that the phases of the moon affect other creatures, including trees, crabs, and other nocturnal animals, the evidence linking moon phases to human behavior is less clear. The idea that the cycle of the moon affects human behavior is called “lunar theory” or the “lunar effect” and that theory has persisted through to modern times, especially regarding nighttime behavior (like sleeping). Urban legends among veteran nurses tell of crazy cases always happening during a full moon – psychotic patients get a little more unsettled, more violence in the ERs… the full moon means chaos to many medical professionals, even now.
But does the moon really affect your behavior or sleep patterns?
One of the strongest associations in popular culture between the moon and behavior is the prevalence of mental illness. For many cultures, the moon has been associated with strange behavior changes: insanity, suicide, violence, and more. The word “lunacy” is even derived from the name Luna, the Roman goddess of the moon.
A study published in the journal Swiss Medical Weekly in 2019 attempted to find a connection between the moon phases and “psychiatric patient admissions, discharges, and length of stay in psychiatric clinics” over a 10-year observational study of data from two psychiatric clinics. However, they came up empty handed: “Despite the widely-held popular belief that the moon affects peoples’ mental health and subsequently psychiatric treatment, our study was unable to support any connection between any phase of the lunar cycle and either admission or discharge rates, nor with length of stay, at psychiatric inpatient clinics.”
Overall, there is very little evidence to suggest that the moon affects human behavior, despite ample anecdotes and a profusion of folklore. The article in Swiss Medical Weekly even offers a rationale for the longevity of these beliefs as a “primal, emotional desire to believe that we are not solely responsible for our own behaviors, rather that some superior force also influences our actions and feelings.”
The evidence that the moon affects your sleep, however, is a little more consistent. In a study published in 2013, volunteers experienced all-around poorer-quality sleep during the full moon. In other studies cited by The Sleep Foundation, some individual facets of the studies contradicted each other, but the ultimate result remained the same: study participants took longer to fall asleep and slept less.
The mechanisms why are debated, however: some argue that the additional moonlight causes difficulty in falling asleep. Some say the moon’s electromagnetic effect can be perceived in humans. Others assert the gravitational pull of the moon affects humans, since humans are mostly made of water. Critics of these rationales argue that the effects of the moon on a human body are often exceptionally small – in the case of the moon’s gravitational pull. Sleep Foundation’s researchers “estimate that the impact of lunar tides on a person measures less than one-millionth the size of an atom.”
All in all, the moon doesn’t have a huge impact on a human’s emotions or behaviors on a day-to-day basis, but a stronger connection between the moon and sleep exists and needs further study.
But while the moon doesn’t influence our behavior directly, it impacts our environment with light, gravity, and magnetism. Some of these aspects affect how we lead our lives: our ability to keep time, how we travel or navigate, and more. And if we’re sleep-deprived, we act differently than when we are fully rested.
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