The idea that full moons trigger strange behavior is one of the most persistent cultural myths, but the scientific evidence firmly contradicts it. A landmark 1986 meta-analysis examining roughly 100 studies found no causal relationship between lunar phenomena and human behavior. More recent large-scale reviews of emergency room data and psychiatric hospital admissions — including studies cited by the NIH — reach the same conclusion: full moons do not produce a measurable increase in ER visits, psychiatric crises, or violent incidents.
Some isolated studies have reported small correlations in narrow subgroups — for example, minor sleep disruptions around the full moon — but these findings are inconsistent, have not been replicated at scale, and fall far short of establishing causation. A 2021 NIH review titled "Moon and Health: Myth or Reality?" surveyed research across multiple health domains and found that superstitions about lunar influence persist despite a lack of supporting evidence. A student-led study published in the Journal of Emerging Investigators similarly found no significant variation in psychiatric admissions across lunar phases.
The persistence of the belief is largely explained by confirmation bias: people notice and remember unusual events that happen to coincide with a full moon, while ignoring the many full moons that pass without incident. The full moon is also the brightest lunar phase, making it more salient and memorable. The broad claim that full moons "cause" unusual behavior commits a correlation-causation fallacy and cherry-picks isolated signals while ignoring the dominant null results from the highest-quality research.