And I do think there's something about the full moon. The police officers I used to work with always said they were in for a rough night when it was a full moon.
Belief in the moon's influence is an ancient one, and common in many cultures including our own. If police and doctors are expecting that full moon nights will be more hectic, they may interpret an ordinary night's traumas and crises as more extreme than usual. Our expectations influence our perceptions, and we look for evidence that confirms our beliefs. (The same thing happens on "bad days" when everything seems to go wrong, but only a few key things actually do.)
Yet carefully controlled studies have not found good evidence supporting this idea.
For example, researchers Ivan Kelly, James Rotton, and Roger Culver, in their study "The Moon was Full and Nothing Happened" (published in the book "The Hundredth Monkey and Other Paradigms of the Paranormal," 1991) examined more than 100 studies of alleged lunar effects and found no significant correlation between phases of the moon and disasters, homicide rates, etc.
Furthermore, there is no known mechanism by which the moon would somehow influence a person's mind to make him more dangerous—except of course for his own expectations.
Still, though the evidence for any direct influence of a full moon is negligible and contradictory, there is some evidence for a less direct (yet more obvious) connection...
There is a good reason why there may be more crime on the nights of a full moon; it has to do with statistics, not lunacy. People are more active during full moons than moonless nights. An especially beautiful full moon may draw families out into the night to appreciate it, and lovers to local necking spots. Muggers and other criminals who ply their trade at night also use the moon's illumination to carry out their crimes. This is the illumination effect theory.
The University of Washington's Chudler has been studying the lunar effect phenomenon for years and has concluded that there are a number of reasons why some studies appear to show a connection between full moons and some forms of human madness or calamity. Either the studies tested a few people over a short period of time, didn't analyze their data with proper statistical tests, or did not take into account when a full moon occurred on a weekend or holiday — a statistically significant factor in altering people's behavior, he said. Some studies include full moon behaviours that occur a few days before and after a full moon, while others concentrate on only a single day.
Chudler explained why it would be virtually impossible to scientifically prove a direct cause-and-effect relationship between full moons and human behavior.
"The one thing to realize about all these studies [that support a connection] is that correlation does not mean causation, even if a [research] paper showed a correlation, which most do not, it wouldn't mean the moon caused the behavior." He said the only way to prove causation would be to put a human on another planet.
"To show causation, we would have to perform an experiment and control all the factors except for the moon," Chudler said. "So, for example, you would take someone to a place with no full moons like on another planet and then compare the behavior to someone in the exact situation where the moon is full."
A touchstone moment for contemporary belief in this myth came in 1978 with the publication of psychiatrist Arnold Lieber's best-seller "Lunar Effects: Biological Tides and Human Emotions," which popularized the gravitational pull theory. In that first edition, Lieber describes how his research led him to fear particularly high levels of trouble during the full moons in January and February of 1974 in Florida, after a study he conducted that purportedly linked the full moon to higher homicide rates in Miami-Dade County, Fla. He writes that he contacted Miami police, media and one hospital administrator to warn them of the expected chaos.
"Sure enough, all hell broke loose," he wrote in a 1996 updated version of the book, retitled, "How the Moon Affects You: A Compelling and Controversial Book on the Awesome Power to Affect Your Emotions and the Way You Live."
What he failed to add was that he'd predicted similar outbreaks of chaos in December 1990 and January 1992, according to a critical review by James Rotton, a Florida psychology professor and well-respected researcher in the field. "Of course these dates passed uneventfully," Rotton writes in "Moonshine," his critical review of Lieber's work for the journal Committee for Skeptical Inquiry.
Another troubling aspect of the book that Rotton challenges cuts to the heart of research supporting the notion of a lunar effect on humans. The original book cites a 1972 study that Lieber and another researcher conducted in which they claim to have found a lunar effect on homicides in Dade County between the years of 1956 and 1970. The book presents a graph that appears to show that homicides in Dade County spiked during full moons, which Lieber wrote that he bases on three studies he conducted that "attained significance," according to Rotton's research.
But Rotton writes that Lieber "neglected to tell readers that [his team] performed 48 tests of significance in all. Not divulging this information is like a gambler failing to tell us how many times a coin was tossed before three heads came up."