The term lunar effect refers to the unfounded belief that there is correlation between specific stages of the Earth's lunar cycle and deviant behavior in human beings that cannot simply be explained by variation in light levels. There is no scientific reason to expect this to be the case, and in spite of numerous studies, no significant lunar effect on human behaviour has been established. Scholars debunking the effect sometimes refer to it as the Transylvanian hypothesis or the Transylvanian effect to emphasise its fanciful nature.
Origins of the belief 
Modern belief in the lunar theory 
Fertility and blood loss 
It is widely believed that the moon has a relationship with fertility due to the corresponding human menstrual cycle, which averages 28 days. However, no connection between lunar rhythms and menstrual onset has been conclusively shown to exist, and the similarity in length between the two cycles is most likely coincidental.
It is sometimes claimed that surgeons used to refuse to operate on the full moon because of the increased risk of death of the patient through blood loss. In October 2009, British politician David Tredinnick asserted that during a full moon "[s]urgeons will not operate because blood clotting is not effective and the police have to put more people on the street.". A spokesman for the Royal College of Surgeons said they would "laugh their heads off" at the suggestion they could not operate at the full moon.
Law and order 
Senior police officers in Brighton announced in June 2007 that they were planning to deploy more officers over the summer to counter trouble they believe is linked to the lunar cycle. Similarly, police in Ohio and Kentucky have blamed temporary rises in crime on the full moon. In January 2008, New Zealand's Justice Minister Annette King suggested that a spate of stabbings in the country could have been caused by the lunar cycle.
It was suggested that the full moon might have influenced voter behavior in the US 2000 presidential election.
Reasons put forward for the belief 
Believers in the lunar theory suggest several different mechanisms by which the behaviour of the moon could influence the behaviour of human beings. A common suggestion is that, since the moon affects large bodies of water such as the ocean (a phenomenon known as "tidal force"), the moon should be expected to have an analogous effect on human beings, whose bodies contain a great deal of water. However, this is a misconception that fails to take into account differences in scale. The tidal force is in fact very weak and should be expected to exercise no more gravitational pull on the human body than a mosquito. A further suggestion is that positive ions increase in abundance during a full moon and that this should be expected to influence human behavior. However, this is a pseudo-scientific claim. Not only is the increase in frequency extremely slight (much smaller than that caused by air conditioning and air pollution), but ionic charge—positive or negative—has no effect on human behavior, and no physiological effect other than static electric shock.
Believers (David Tredinnick being a prominent example) often support their claims by noting that many police officers and nurses have observed a lunar effect in the course of their work. To the extent that nurses and police officers do indeed claim to observe patterns, this is most likely to be explained in terms of confirmation bias: People notice if something dramatic happens during a full moon, but do not notice when nothing dramatic happens; furthermore, dramatic occurrences that do not occur during full moons are typically not counted as evidence against the belief. Believers are further bolstered in their belief through communal reinforcement: The more people talk about the effect, the more people notice spurious relationships.
Scientific research on the theory 
Some studies seem to offer limited support for lunar effects, but most fail to show any relationship between the phase of the moon and abnormal behaviour, and meta-analyses have revealed that apparently significant results are likely to be statistic anomalies rather than indicative of a real effect. In general, apparent positive findings have tended to be inconclusive, contradicted by other studies, or shown to be the result of statistical errors. For example, one study found a statistically significant correlation between lunar phase and hospital admissions due to gastrointestinal bleeding, but researchers acknowledged that the wide variation in the number of admissions throughout the lunar cycle limited the interpretation of the results. Two other studies found evidence that those with mental disorders generally exhibit periods of increased violent or aggressive episodes during the full moon, but a more recent study found no such correlation. An analysis of mental-health data found a significant effect of moon phase, but only on schizophrenic patients. Nor are such effects necessarily related directly to the behaviour of the moon. A study into epilepsy found a significant negative correlation between the mean number of seizures and the fraction of the moon illuminated by the sun, but this correlation disappeared when the local clarity of the night sky was controlled for, suggesting that it was the brightness of the night that influenced the occurrence of epileptic seizures.
A reported correlation between moon phase and the number of homicides in Dade County was found, through later analysis, not to be supported by the data and to have been the result of inappropriate and misleading statistical procedures.
Three studies carried out between 1959 and 1973 reported a 1 percent increase in births in New York following a full moon. However, a 1957 analysis of 9,551 births in Danville, PA, found no correlation between birth rate and the phase of the moon, and a 2001 analysis of 70,000,000 birth records from the National Center for Health Statistics revealed no correlation between an increased birth rate and the full moon phase.
A meta-analysis of thirty-seven studies that examined relationships between the moon's four phases and human behavior revealed no significant correlation. The authors found that, of twenty-three studies that had claimed to show correlation, nearly half contained at least one statistical error. Similarly, in a review of twenty studies examining correlations between Moon phase and suicides, most of the twenty studies found no correlation, and the ones that did report positive results were inconsistent with each other.
See also 
- Carroll, Robert Todd (12 August 2011). "Full Moon and Lunar Effects". The Skeptic's Dictionary. Retrieved 22 October 2011.
- Adams, Cecil (13 March 1987). "Do things get crazy when the moon is full?". The Straight Dope. Retrieved 14 December 2011.
- Iosif, A. & Ballon, B. (2005). Bad moon rising: the persistent belief in lunar connections to madness. CMAJ, 173, 1498-1500.
- Harper, Douglas. "Lunatic". The Online Etymological Dictionary. Retrieved 2011-12-13.
- Adams, Cecil (24 September 1999). "What's the link between the moon and menstruation?". The Straight Dope. Retrieved 14 December 2011.
- Roman, E.M., Soriano, G., Fuentes, M., Luz-Galvez, M.,Fernandez, C. (2004) The influence of the full moon on the number of admissions related to gastrointestinal bleeding. International Journal of Nursing Practice. Vol. 10;6, p296.
- Hansard, 14 Oct 2009 : Column 414
- Ian Douglas (October 11, 2010). "MPs believe the funniest things". Daily Telegraph. Retrieved 2010-10-18.
- Attewill, Fred (2007-06-05). "Police link full moon to aggression". The Guardian (London). Retrieved 2010-05-11.
- toledoblade.com - Analysis shines light on full moon, crime
- Skeptic's Dictionary and Refuge: Mass Media Bunk
- "Police busy for full moon". The Kentucky Post (E. W. Scripps Company). 2002-01-29. Archived from the original on 2007-07-06.
- "Link between moon and crime supported - national". Stuff.co.nz. 2008-02-07. Retrieved 2011-07-11.
- #Y127; 24% of the U.S. Presidential Vote swayed by the Full Moon effect
- Novella, Steven. "Pseudoscience Sells". Retrieved 03/20/12.
- Chulder, Eric. "Moonstruck! Does the full moon influence behavior?". Neuroscience for Kids. University of Washington. Retrieved December 2011.
- Kelly, Ivan; Rotton, James; Culver, Roger (1986), "The Moon Was Full and Nothing Happened: A Review of Studies on the Moon and Human Behavior", Skeptical Inquirer 10 (2): 129–43. Reprinted in The Hundredth Monkey - and other paradigms of the paranormal, edited by Kendrick Frazier, Prometheus Books. Revised and updated in The Outer Edge: Classic Investigations of the Paranormal, edited by Joe Nickell, Barry Karr, and Tom Genoni, 1996, CSICOP.
- Roman, E. M.; Soriano, G.; Fuentes, M.; Luz-Galvez, M.; Fernandez, C. (2004). "The influence of the full moon on the number of admissions related to gastrointestinal bleeding". International Journal of Nursing Practice 10 (6): 296.
- Drum, M.; Terry, C.; Hammonds, C. (1986). "Lunar phase and acting-out behaviour". Psychological Reports 59: 987–990.
- Lieber, A. "Human aggression and the lunar synodic cycle". Journal of Clinical Psychiatry 39 (5): 385–392.
- Owen, C.; Tarantello, C.; Jones, M.; Tennant, C. (1998). "Lunar cycles and violent behaviour". Australian and New Zealand Journal of Psychiatry 32 (4): 496–499.
- Barr, W. (2000). "Lunacy revisited: The influence of the moon on mental health and quality of life". Journal of Psychosocial Nursing and Mental Health Service 38: 28–36.
- Baxendale, S.; Fisher, J. (2008). "Moonstruck? The effect of the lunar cycle on seizures". Epilepsy and Behavior 13 (3): 549–550.
- Abell, George; Greenspan, Bennett (1979), "The Moon and the Maternity Ward", Skeptical Inquirer 3 (4): 17–25 Reprinted in Paranormal Borderlands of Science, edited by Kendrick Frazier, Prometheus Books, ISBN 0-87975-148-7.
- Caton, Dan (2001). Natality and the Moon Revisited: Do Birth Rates Depend on the Phase of the Moon?, Bulletin of the American Astronomical Society, Vol 33, No. 4, 2001, p. 1371. Overview of the paper.
- Marshall, Konrad (2007-05-02), "Must be a Full Moon", The Florida Times-Union: C–1
- Abell, George (1979). Review of the book The Alleged Lunar Effect by Arnold Lieber, Skeptical Inquirer, Spring 1979, 68-73. Reprinted in Science Confronts the Paranormal, edited by Kendrick Frazier, Prometheus Books, ISBN 0-87975-314-5.
- Abell, George and Barry Singer (1981). Science and the Paranormal - probing the existence of the supernatural, Charles Scribner's Sons, chapter 5, ISBN 0-684-17820-6.
- Berman, Bob (2003). Fooled by the Full Moon - Scientists search for the sober truth behind some loony ideas, Discover, September 2003, page 30.
- Caton, Dan (2001). Natality and the Moon Revisited: Do Birth Rates Depend on the Phase of the Moon?, Bulletin of the American Astronomical Society, Vol 33, No. 4, 2001, p. 1371. A summary of the results of the paper.
- Diefendorf, David (2007), Amazing... But false! Hundreds of "facts" you thought were true, but aren't, Sterling Publishing, ISBN 978-1-4027-3791-6
- Sanduleak, Nicholas (1985). The Moon is Acquitted of Murder in Cleveland, Skeptical Inquirer, Spring 1985, 236-42. Reprinted in Science Confronts the Paranormal, edited by Kendrick Frazier, Prometheus Books, ISBN 0-87975-314-5.
- The Skeptic's Dictionary on the lunar effect
- Straight Dope article
- Dan Caton, Birth Rates and the Phase of the Moon
- Madness and the Moon
- University of Leeds study on the Transylvanian effect
- Belief, Perceptions, and Full Moons at a Psychiatric Hospital