The Moon’s influence on our planet is undeniable. Its gravity pulls the waters of our oceans, creating the tides. Its light cues the migration of birds, the foraging of wildebeests, and the synchronized mating of corals. It is not surprising, then, that since ancient times, humans have wondered if the cycle of the Moon might exert similar power over our minds.
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Some of the earliest records of the purported link between the Moon and madness can be found in ancient Greek and Roman texts. An oft-repeated saying, attributed to the 5th-century bc physician Hippocrates, claims that “One who is seized with terror, fright, and madness during the night is being visited by the Goddess of the Moon.” Pliny the Elder, a Roman author and natural philosopher, wrote that the Moon, “with her winding and turning in many and sundry shapes, hath troubled much the wits of the beholders.” He conjectured that the full Moon caused more dew to form, leading to increased moisture in the brain. The very word “lunatic” comes from Latin lunaticus, from the Latin word for the Moon, luna. People with mental illnesses and such neurological disorders as epilepsy were said to be “moonstruck,” rendered mad by lunar influence.
It is not surprising, then, that since ancient times, humans have wondered if the cycle of the Moon might exert similar power over our minds.
The belief continued through the medieval and early modern periods in Europe. At the turn of the 17th century, Shakespeare wrote in Othello: “It is the very error of the moon; She comes more near the earth than she was wont, And makes men mad.” And the Moon’s phases in particular were referenced by the English legal expert William Blackstone in the 18th century: “A lunatic, or non compos mentis, is properly one who hath lucid intervals, sometimes enjoying his senses and sometimes not and that frequently depending upon the changes of the moon.” Mental health patients at London’s Bethlehem Hospital (also known as Bedlam) were chained and beaten at certain phases of the Moon to prevent violence, a practice that went on (according to a 1943 article in the American Journal of Psychiatry) until 1808.
While medieval and early modern Europe had plenty of werewolf lore, a transformation triggered by the full Moon is missing from most of these stories. One of the few stories to mention the Moon at all, from 13th-century writer Gervase of Tilbury, claimed that the werewolf Chaucevaire transformed at the new Moon. The full Moon trope did not really take off until the film Frankenstein Meets the Wolf Man was released in 1943. In it, the titular werewolf, who had been killed in the original 1941 The Wolf Man, is resurrected when the light of a full Moon hits his longdead body; he transforms into a wolfish creature at the next full Moon. Countless books, movies, TV shows and video games released since then have included full-Moon werewolf transformations. It even crops up in works outside the traditional horror genre, such as the Harry Potter book and film series and the music video to Michael Jackson’s “Thriller” (1982).
Contemporary vampire stories have largely lost their historic connections to the Moon, but the first major such tale to be published in English, John William Polidori’s The Vampyre (1819), includes the revival of a vampire when he is “exposed to the first cold ray of the Moon that rose after his death.”
Rumors about the power of the full Moon have persisted into the 21st century. Anecdotal evidence about monthly spikes in crime, unruly classrooms, and busy hospital emergency departments abound on such internet forums as Reddit, with threads on teacher forums titled “The FULL MOON is making my kids crazy!!!” and security guards asking each other, “You guys dealing with full moon bs too?”
In recent decades, countless scientists have attempted to pinpoint a connection between the Moon and unruly or otherwise strange behavior. In 1992, a paper published in the journal Psychological Reports analyzed twenty previous studies examining a link between the cycle of the Moon and suicidal behavior. The authors concluded: “Most studies indicated no relation between lunar phase and the measures of suicide. The positive findings conflicted, have not been replicated, or were confounded with variables such as season, weekday, weather, or holidays….there is insufficient evidence for assuming a relationship between the synodic lunar cycle and completed or attempted suicide.” Similarly, a 2010 study in the Journal of Criminal Justice examined police data over a five-year period; it found no link between criminal activity and the phases of the Moon. In a 2009 article for Scientific American, psychologists Dr. Hal Arkowitz and Dr. Scott Lilienfeld summarized their analysis of studies on the Moon’s effects on the human psyche thus: “The lunar lunacy effect appears to be no better supported than is the idea that the moon is made of green cheese.”
The Moon has demonstrated its power over the human mind through our never-ending stories and legends about it.
However, some researchers insist that there is more to the story.
© Rijksmuseum, Amsterdam. A werewolf terrorizes children in this woodcut by Lucas Cranach the Elder, entitled The Werewolf or The Cannibal (c. 1510–12).
A 2021 study published in the journal Science Advances demonstrated a correlation between the lunar cycle and the circadian rhythms that govern wakefulness. The connection appeared in remote communities in Argentina that lacked electric lights, as well as in urban Seattle (though the effects were stronger in Argentina, where the study participants lost up to an hour and a half of sleep on nights preceding the full Moon). Since lack of sleep can exacerbate some mental health conditions, including bipolar disorder, some have argued that the full Moon’s brightness might have been a contributor to some episodes of supposed “lunacy,” especially in historical accounts before artificial light pollution began outshining the Moon’s gentle gleam.
Other researchers have spotted correlations between the Moon and the mood cycles of people with bipolar disorder. In 2018, Dr. Thomas Wehr published a study on seventeen individuals with rapid cycling bipolar disorder, a pattern of four or more manic or depressive episodes within one year. Over the course of an average of 1.6 years’ worth of observations of each patient, he found that all of these patients’ mood cycles were synchronous, at some point, with subtle and complex aspects of the Moon’s cycle, including its effects on the tides. However, there was no singular lunar phase or position that affected all of the patients—the subjects did not, for example, all experience mania around the full Moon. (The mechanism by which people’s brains “sense” these lunar cycles remains unknown, as does the reason why the different patients seemed to sync with different aspects of lunar behavior.)
While the bulk of scientific evidence opposes a link between the full Moon and “lunacy,” the debate is far from settled. If nothing else, the Moon has demonstrated its power over the human mind through our never-ending stories and legends about it.
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From Lunar: A History of the Moon in Myths, Maps, and Matter, edited by Matthew Shindell. Published by the University of Chicago Press. Copyright © 2024. All rights reserved.
