Full Moon Rising
Note: An excerpt from my upcoming book, Escaping the Fact-Free Zone: Using Critical Thinking to Survive the 21st Century.
For centuries, many have shared stories of humans shapeshifting into werewolves at the first sight of a full moon. While werewolves are today primarily relegated to the realm of fiction, the mystique of the full moon persists. As some law enforcement personnel insist, is there more crime on a full moon? Are more babies born on a full moon, as most believe? Are these and other effects attributed to the full moon legitimate science or the fruits of overactive imaginations?
Pseudoscience encompasses a range of beliefs and practices that claim to be scientifically based but lack rigorous, controlled scientific investigation. The beliefs have infiltrated almost every facet of American life, including police departments and hospitals. On one occasion, while completely bored during a brief hospital stay, I conducted a short, unscientific survey. I asked healthcare professionals if they believed more babies were born on a full moon, and the vast majority replied affirmatively. One nurse was convinced, saying that an emergency room on a full moon was “one crazy place,” with more accidents and women in labor than usual. Another study of mental health professionals found that four out of five believed that there was a relationship between the full moon and human behavior and mental illness. (Francis) These individuals should know! For most, this would constitute conclusive proof that the full moon affects human behavior and childbirth. There is only one problem. When examined scientifically, the data reveal no statistically significant connection.
While many cite anecdotal evidence that more babies are born on a full moon, scientific research does not support this claim. Visit any large emergency room on any evening, and one will likely find a woman in labor. I volunteered in a city emergency room on Friday nights years ago; it was “exhausting.” When a woman in labor came in, confusion often became chaos, and it’s easy to see that one who believes in the full moon’s impact on labor could see that belief reinforced.
I once had an eighth-grade student do a science project on the topic. She obtained birth data from three Eastern Shore hospitals for six months. To her credit, she spent considerable time crunching all the numbers. Part of the problem she encountered was that it is often hard to associate a full moon with a particular evening because the moment the moon becomes full can happen at any time during the twenty-four-hour day. She identified three-day periods around the full moon, new moon, first quarter, and last quarter, and then tallied the number of births in each period. There was a month or two at a particular hospital when the number of full-moon births was slightly higher, but there were also months when it was lower. There was no statistically significant difference when data from the three hospitals and the six months were pooled. Nurses at the three hospitals were surprised by the results, as each had expected more births during full moon periods.
A more substantial Spanish study analyzed data spanning more than 120 years and found no increase in births during full moons. (Marco-Gracia) One fallacy in looking at small amounts of data is that one can see aberrations in the normal probabilities. Flip a coin ten times, and one will likely get more heads or tails. But over thousands of flips, the numbers will even out. In another study, half a million North Carolina births showed no relationship. (Arliss) Studies also show no relationship between the full moon and aberrant behavior.
The supposed connection between the moon and behavior dates back to the ancient Greeks and Romans, and the Moon plays a prominent role in many cultures. The term for a person behaving abnormally is “lunatic,” which shares the same root as our term for the Moon, “lunar,” derived from Luna, the Roman goddess of the Moon. Police departments have even been known to deploy additional personnel on a full moon. Hollywood has fostered the myth that many murders, monsters, and strange happenings are connected with a full moon. This is pseudoscience at its best; myths are perpetuated with virtually no one checking to see if the data back them up. The connection seems so believable in theory that many see no reason to question it.
An often-used line of explanation focuses on the human body's water, suggesting that the full moon's tidal effect on bodily fluids could influence behavior. It’s a nice-sounding argument until one realizes a mosquito on one’s arm has a more significant gravitational effect on the body fluid than a full moon. Does that mean mosquitoes increase the chance of childbirth? There is some evidence that full moons might affect sleep patterns, not surprisingly, since increased light could slightly affect one’s circadian rhythm.
Many of the teachers I taught with believed there was more student misbehavior on a full moon. At our school, the disciplinary records never bore this out, but the belief persisted. I noted an increase in restlessness and time-on-task on the day or two after Halloween, but increased sucrose consumption might have contributed to this.
A 1982 traffic study in one town found more accidents on nights with a full moon. However, the analysis showed that a statistically significant number of full moons occurred on weekends, when more people were driving. (Arkowitz) There are many poorly designed studies and experiments like this. This is why research replication is critical. Pseudoscience often cites weak or flawed studies, but science considers all relevant research. If the results of a study can’t be replicated, it behooves us to cast that aside.
Hollywood will always delight in perpetuating the full-moon myth. It’s hard to see anything on a new moon, and while this might be terrifying to those frightened of the dark, it makes for lousy cinematography. But filming on a night with a full moon with some illumination and “ghostly” shadows, one can see just enough to fuel the imagination. Our obsession with werewolves and other full moon legends makes it easy to understand our fascination with those eerie nights. Go out into the woods on a full moon when the hoot of an owl fractures the silence, the rustling of leaves makes you jump, and those shadows put your imagination in high gear. Emotion will quickly trump reason. At those moments, one could believe just about anything.
Why do so many professionals believe in the full moon’s impact on behavior? This is a classic example of Confirmation Bias, where one focuses on data that conforms to one's beliefs while overlooking data that does not. Nurses in a hospital see many births, and a few occur on a full moon. If they believe births are more likely to occur on a full moon, they will likely make note of full moon births while likely overlooking non-full moon births. Remembering primarily births occurring on full moons leads one to think they occur more often on those nights. They are more likely to remember events that align with their beliefs than to examine them objectively. If I think I have a lucky hat, I’ll remember all the times something good happened while wearing it, while overlooking good happenings when not wearing it.
Sources:
Arkowitz, Hal; Lilienfeld, Scott. “Facts and Fictions in Mental Health: Lunacy and the Full Moon.” Scientific American, March 2009. http://www.scientificamerican.com/article/lunacy-and-the-full-moon/.
Arliss, J.M.; Kaplan, E.M.; Galvin, S.L. The effect of the lunar cycle on frequency of births and birth complications.” American Journal of Obstetrics and Gynecology, 2005 May;192(5): pp.1462-4. (Abstract in National Institute of Health, US National Library of Medicine, “ http://www.ncbi.nlm.nih.gov/pubmed/15902138.)
Francis, O.J.; Kopke, B.J.; Affatato, A.J.; Jarski, R.W. “Psychiatric Presentations During All 4 Phases of the Lunar Cycle.” Advances in Mind-Body Medicine, 2017; 31(3), pp. 4-7. (Abstract in National Library of Medicine, https://pubmed.ncbi.nlm.nih.gov/28841578/.)
Heshmat, Shahram. “What is Confirmation Bias?” Psychology Today, 23 Apr 2015. https://www.psychologytoday.com/us/blog/science-of-choice/201504/what-is-confirmation-bias.
Marco-Gracia, F.J. “The influence of the lunar cycle on spontaneous deliveries in historical rural environments.” European Journal of Obstetrics & Gynecology and Reproductive Biology, 2019
Rotton, J. and Kelly, I. “Much Ado about the Full Moon: A Meta-analysis of Lunar-Lunacy Research.” Psychological Bulletin, Vol. 97, No. 2, March 1985, pp. 286–306.