The full moon increases crime and ER visits
Decades of research have found no reliable link between full moon phases and emergency room visits, violent crime, psychiatric hospital admissions, or other behavioral outcomes. The persistent belief in lunar effects on behavior is better explained by confirmation bias and selective memory than by any actual pattern in the data.
What we know
The idea that the full moon influences human behavior, contributing to increased aggression, accidents, psychiatric crises, or general "madness," traces back centuries and gave rise to the English words "lunatic" and "lunacy," derived from "luna," the Latin word for moon. This etymological history reflects genuinely old cultural beliefs rather than modern scientific findings, and the persistence of the idea into the present day is largely a matter of cultural transmission rather than accumulated evidence.
Systematic scientific investigation of the lunar effect claim goes back decades and has been remarkably consistent in its conclusions. A frequently cited comprehensive review examining dozens of published studies covering psychiatric hospital admissions, crisis center calls, suicide rates, and other behavioral measures found no significant relationship with lunar phase across the large majority of studies reviewed. Subsequent research examining emergency department visits, including studies looking specifically at trauma admissions, psychiatric emergency presentations, and animal bite incidents, has continued to find no statistically significant pattern tied to the full moon once proper statistical controls are applied.
One especially well-known and frequently cited study examined whether the full moon was associated with increased violent crime using several years of police and hospital data, and found no meaningful association once other factors, including weekend timing, weather, and seasonal patterns, were properly accounted for. Where earlier studies did occasionally report a positive lunar effect, subsequent re-analyses using more rigorous statistical methods and larger sample sizes often failed to replicate the finding, a common pattern in psychological research known as the decline effect, where initially reported effects shrink or disappear as more and better data accumulates.
Psychologists studying why the lunar myth persists despite this consistent lack of evidence point to confirmation bias as the central mechanism: people who already believe in a full moon effect tend to notice and remember unusual or chaotic events that happen to occur near a full moon, while readily forgetting or failing to register the far more numerous unusual events that occur during other lunar phases, or the ordinary, uneventful nights that also happen to coincide with a full moon. This selective attention creates a powerful subjective impression of a pattern that does not hold up when data is collected systematically and compared across all lunar phases rather than recalled anecdotally. A well-documented related study found that hospital staff who believed in the lunar effect reported perceiving more disturbed patient behavior on full-moon nights even when the actual, objectively recorded behavioral incident rates showed no such increase, providing a direct demonstration of the belief itself shaping perception independent of underlying reality.
There is a very small amount of legitimate scientific interest in more limited and specific lunar-related biological questions, such as research into whether moonlight brightness affected human sleep patterns before the widespread availability of artificial lighting, an effect that some limited historical and small-sample modern data suggest may have existed to a modest degree in specific circumstances. This narrow area of ongoing scientific curiosity is a distinct and separate question from the broad, dramatic behavioral and psychiatric claims embedded in the popular "lunar lunacy" myth, and should not be used to lend it unwarranted credibility. The overwhelming weight of accumulated research across psychiatry, emergency medicine, and criminology finds no reliable full moon effect on human behavior of the kind the folklore describes.
Common claims
- Full moons increase psychiatric hospital admissions.Not supported
- Full moons increase violent crime rates.Not supported
- Full moons increase emergency room visits.Not supported
- Belief in lunar effects is driven by confirmation bias.Accurate
Evidence hierarchy
All sources
- The moon and madness reconsideredJournal of Affective Disorders / PubMed · 1996
- Lunar phase and psychiatric emergenciesPubMed / National Library of Medicine · 2019
- Full moon and crisis behavior: a reviewAmerican Psychological Association · 2020
- Does the full moon really affect behavior?Scientific American · 2021