“People become more aggressive during a full moon.”

The notion that a full moon influences human behavior, particularly by making people more aggressive, is a deeply ingrained belief with ancient origins. This idea, often termed the "lunar effect," has roots in folklore and historical thought. The very word "lunatic" stems from the Latin "lunaticus," meaning "moonstruck," reflecting a long-held conviction that the moon's phases could trigger madness or erratic behavior. Ancient thinkers like Aristotle and Pliny the Elder even speculated that the moon's influence on the brain's moisture mirrored its effect on ocean tides.

Despite the popular appeal of this myth, extensive scientific investigation has consistently debunked any direct correlation between lunar phases and human aggression or other behaviors. Numerous studies and meta-analyses, which combine the results of many individual research efforts, have found no statistically significant link between the full moon and crime rates, psychiatric admissions, or other measures of unusual human activity. While some earlier studies occasionally reported a connection, these findings often suffered from methodological flaws or could not be replicated by more rigorous subsequent research.

The persistence of this myth largely comes down to psychological phenomena like confirmation bias and selective memory. People are more likely to notice and remember unusual or aggressive incidents that happen to coincide with a full moon, while easily forgetting the countless times strange events occur during other lunar phases or when nothing out of the ordinary happens under a full moon. This selective recall reinforces the existing belief. Furthermore, professionals in high-stress fields, such as emergency services, might subconsciously attribute chaotic shifts to the full moon, which can serve as a coping mechanism for challenging situations. Historically, brighter moonlight may have also disrupted sleep patterns, potentially leading to increased irritability, which could have contributed to the initial formation of the myth.