Does a Full Moon Affect Human Behavior?

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  • Many emergency-room doctors, firefighters and police officers enjoy swapping stories about the crazy accidents and incidents that take place on nights when the sky is enlivened by a full moon, blaming lunar cycles for the perceived uptick in unusual activity
  • Belief in a “lunar effect” and the intermittent insanity associated with it dates back to the Middle Ages when some believed humans could be transformed into vampires or werewolves under a full moon
  • While anecdotal evidence may lead you to believe there are more accidents, crimes, drug overdoses, ER visits, hospitalizations and suicides on nights featuring a full moon, scientific research has failed to prove a full moon has any bearing on human behavior
  • One small study to the contrary suggests your body and sleep may be affected by a full moon — resulting in it taking you longer to fall asleep, causing you to sleep less and producing less deep sleep

By Dr. Mercola

This natural phenomenon takes place once every 29.53 days, or roughly once a month. As it did in March 2018, it sometimes appears twice a month. It occurs when the moon is completely illuminated by the sun's rays as a result of the Earth being nearly directly aligned between the sun and the moon. By now, you probably know what it is: a full moon.

Urban legend suggests the full moon brings out the worst in both people and situations. If you talk to emergency room (ER) personnel, firefighters, paramedics and police officers, they very likely will share a story or two about the "lunacy" that occurs on nights when the sky is enlivened by a full moon.

By the way, the word lunacy and a related term "lunatic," which was coined in the mid-16th century to refer to a temporary insanity in humans attributable to changes in the moon, have their origin in the Latin root "luna," which means moon.

According to Scientific American, "Belief in the 'lunar lunacy effect,' or 'Transylvania effect,' as it is sometimes called, persisted in Europe through the Middle Ages, when humans were widely reputed to transmogrify into werewolves or vampires during a full moon."1 But is it true? Does a full moon negatively affect human behavior? Let's take a closer look at the facts.

The Full Moon Has Been Said to Cause Accidents, Crimes, Suicides and More

Eric Chudler, Ph.D., a research associate professor in the department of bioengineering at the University of Washington in Seattle, has compiled research highlighting possible links between a full moon and human behavior. Below are the major categories of activities and experiences noted by Chudler that have been associated with increased activity during a full moon:2

Anxiety and depression

Animal bites

Accidents

Crime

Drug overdoses

ER visits

Hospital admissions

Suicides

Violence and aggression

According to Chudler, while urban legend persists, the scientific results related to how full moons affect human behavior are somewhat inconclusive. He states:3

"Perhaps one of the first things you notice about [lunar] studies is that the results are inconsistent. Some studies show a particular behavior will occur more often during the full moon and other studies show no relationship between the behavior and the full moon.

Although most experiments fail to show a relationship between the phase of the moon and abnormal behavior, the belief in the 'lunar effect' is still strong among many people. Unfortunately, the occasional newspaper story that describes strange behaviors during a full moon only reinforces this myth."

German Researchers Debunk Influence of Friday the 13th, Full Moons and Zodiac Signs

While anecdotal evidence may suggest a full moon triggers strange human behavior, such as more ER visits, more psychiatric admissions and more traffic accidents, the scientific evidence doesn't seem to support the belief there is a so-called "dark side of the moon" when it is full.4

For example, a 2011 study published in the World Journal of Surgery suggests that while a significant portion of medical staff believe lunar phases can affect human behavior, the evidence does not support such a conclusion. The study authors said:5

"The influence of superstition, moon calendars and popular belief on evidence-based medicine is stunning. More than 40 percent of medical staff is convinced that lunar phases can affect human behavior. The idea that Friday the 13th is associated with adverse events and bad luck is deep-rooted in the population of Western industrialized countries. The­ aim of the present study was to test the hypothesis that these myths are transferable to real-life surgery."

After analyzing operation records of nearly 28,000 patients who underwent some type of surgery during a nine-year period from August 2001 and August 2010 — a period punctuated by 111 full moons — researchers at University Hospitals of Saarland in Homburg/Saar, Germany, found patient characteristics did not differ with respect to lunar phases, zodiac signs or occurrences of Friday the 13th. The study authors said:6

"Full moon phases, the presence of Friday the 13th and zodiac signs influenced neither intraoperative blood loss nor emergency frequency. No statistical peaks regarding perforated aortic aneurysms and gastrointestinal perforations were found on a full moon or Friday the 13th.

Scientific analysis of our data does not support the belief that moon phases, zodiac signs or Friday 13th influence surgical blood loss and emergency frequency. Our data indicate such beliefs are myths and far beyond reality."

Research Aside, Doctors and Police Subscribe to 'Full Moon Madness'

Regardless of the scientific evidence, many doctors, such as Dr. John Becher, past president of the American Osteopathic Association and current treasurer of their board of trustees, believe the full moon has a very real effect on the ER.

Having practiced emergency medicine for nearly 40 years, including more than 30 years as residency director of emergency medicine at the former City Avenue Hospital and Albert Einstein Medical Center in Philadelphia, Becher noticed changes in the 11-bed psychiatric emergency center area during full moons.

"You could almost tell the phase of the moon by how crowded that area … was," says Becher. "Anytime the moon was full, that area was overflowing."7 Dr. Paul Allegretti, program director for emergency medicine residency at Midwestern University-Chicago College of Osteopathic Medicine in Downers Grove, Illinois, also believes the ER seems busier when the moon is full. "I think people are sicker and it seems like more unusual things happen when the moon is full, though I don't think I could ever prove it," he says.8

According to BBC News, police in Brighton employed extra officers during full moons after research in 2007 suggested an increase in violent incidents when the moon was full.9 The late Andy Parr, a Brighton inspector, said, "From my experience, over 19 years of being a police officer, undoubtedly on full moons, we do seem to get people with … stranger behavior [who are] more fractious [and] argumentative. And I think that's something that's been borne out by police officers up and down the country for years."10

Not All Doctors Are Convinced the Full Moon Matters

A 2004 study published in the Indian Journal of Medical Science11 suggests a full moon has little or no direct bearing on ER admissions. Researchers from the Sina Trauma and Surgery Research Center in Tehran analyzed more than 54,000 patient cases, representing trauma admissions to three Tehran-based hospitals, during a 13-month time period. About the relationship between rate of admissions and full moons, the study authors said:12

"In our study the number of trauma patients was not increased during the full moon days [as compared to] other days of the lunar month. Statistical analyses of data didn't exhibit a positive relationship between full moon days and increased trauma patient admission to ERs. An association between assault and attempted suicide was not observed around the full moon days either … and [neither was there an] increase in severity of traumatic injury sustained during full moon days."

In terms of anecdotal evidence, the aptly named Dr. Eric Moon, an ER physician who has more than 12 years' experience working the night shift at St. Bernard Hospital in Chicago, ascribes little value to urban legends linking medical events and full moons.

"For as long as I've worked in the emergency department, whenever there's a full moon, invariably someone will make a comment about how it's going to be a rough night," he said. While his co-workers buy into the full moon myth, Moon thinks attempts to link lunar phases with ER work have little merit. "We frequently have crazy nights in the ER when the moon is full because that's just the nature of the ER, no matter what phase the moon is in," he noted.13

Dental Events Also Shown To Be Unaffected by Lunar Cycles

While you may hear a lot about how a full moon can affect physical health, what might its effects be on oral health? Can a full moon impact what's going on inside your mouth? A 2015 study published in BMC Oral Health14 suggests there is no observable relationship between the occurrence of odontogenic abscesses (OA), also known as tooth abscesses, and lunar phases.

In the study, a group of German researchers analyzed the records of more than 1200 patients who experienced a dental emergency during 2012. All patients were surgically treated at the AllDent Dental Center emergency unit in Munich. The incidence of tooth abscess was correlated to "daily meteorological data, biosynoptic weather analysis and cyclic lunar activity." Based on their analysis, the study authors concluded:15

"There was no seasonal variation in OA incidence. None of the meteorological parameters, lunar phases or biosynoptic weather classes were significantly correlated with OA incidence, except the mean barometric pressure, which was weakly correlated … There is no evidence supporting a correlation between the incidence of OA and the weather or lunar activities."

Can a Full Moon Affect Your Sleep?

If you've ever wondered if a full moon affects your sleep, scientists from Switzerland's University of Basel may have the answer. As noted in the journal Current Biology,16 their 3.5-day study involved 33 volunteers who were not told of the purpose of the research, nor could they see the moon from their beds. The research was conducted in a dark room inside a sleep lab under close supervision. In terms of a so-called "lunar influence" on sleep, during a full moon the researchers noted the participants:17

  • Took five minutes longer to fall asleep
  • Experienced 20 minutes less sleep, as assessed by an electroencephalogram (EEG)
  • Spent 30 percent less time in non-rapid eye movement (NREM) deep sleep, which was also assessed by EEG

The study authors noted those changes were associated with an overall decrease in subjective sleep quality as well as diminished endogenous melatonin levels. About the research, they stated, "This is the first reliable evidence that a lunar rhythm can modulate sleep structure in humans when measured under the highly controlled conditions of a circadian laboratory study protocol without time cues."18

Professor Christian Cajochen, Ph.D., head of the center for chronobiology at the University of Basel and one of the study authors, added, "The lunar cycle seems to influence human sleep, even when one does not see the moon and is not aware of the actual moon phase."19

While some suggest poor sleep may come from the moon being brighter when it's full, the current study controlled for brightness. This factor seems to suggest that you cannot manage potential full moon-related sleep issues simply by wearing an eye mask or using blackout curtains.

U.K. sleep expert Neil Stanley, Ph.D., says he found the University of Basel study intriguing. That said, he also believes more research is needed with a larger group of individuals over a longer period of time to substantiate any potential lunar effects on sleep. "It's one of those things you would instinctively believe, so to actually find an effect is interesting," he said. "Unfortunately, there has been no further research in this area since that study."20

Given the interest in blue moons and super moons these days, Stanley suggests some of the sleep issues linked to full moons might just be due to its brightness and size. After all, you are less likely to notice a crescent moon and therefore unlikely to attach your sleep problems to it. Such realities, he suggests, could be "an example of confirmation bias — where people are more likely to notice and remember information that fits with their beliefs."21

The Bottom Line About a Full Moon's Effects

As you can see, the opinions about how a full moon may affect human life vary widely. While anecdotal information suggests "the lunar effect" is real and is noticeable on a regular basis, scientific evidence fails to attribute clear physical cause.

The common perception that more accidents, crimes, medical emergencies, violence and other terrible events happen under a full moon are just that, perceptions. In an attempt to describe how people perceive a full moon, a pair of scientists coined the term "illusory correlation," which Scientific American describes as:22

"[T]the perception of an association that does not in fact exist. Illusory correlations result in part from our mind's propensity to attend to — and recall — most events better than nonevents. When there is a full moon and something decidedly odd happens, we usually notice it, tell others about it and remember it.

We do so because such co-occurrences fit with our preconceptions. In contrast, when there is a full moon and nothing odd happens, this nonevent quickly fades from our memory. As a result of our selective recall, we erroneously perceive an association between full moons and myriad bizarre events."

As noted by The Washington Post, "No one has ever been able to show consistently, with multiple studies, that the full moon has any effect on behavior."23 Until research is presented to overturn this fact, it's best to simply enjoy a full moon as a natural wonder and object of beauty. In terms of any unusual events that may coincide with a full moon — I suggest you take them at face value and embrace them as part of the human experience as you would any other night, moon or no moon.