Lunar phase (or Moon phase) refers to the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases vary cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun. One half of the lunar surface is always illuminated by the Sun (except during lunar eclipses), and is hence bright, but the portion of the illuminated hemisphere that is visible to an observer can vary from 100% (full moon) to 0% (new moon). The boundary between the illuminated and unilluminated hemispheres is called the terminator.The lunar effect is a theory which overlaps into sociology, psychology and physiology suggesting that there is correlation between specific stages of the Earth’s lunar cycle and deviant behavior in human beings. It is a pseudoscientific theory, however. The claims of a correlation of lunar phases to human behavior do not hold up under scientific scrutiny.
Over the past 30 years, even more evidence has emerged to stress that this is pseudoscience. The theory is sometimes also referred to as the Transylvanian hypothesis or the Transylvanian effect in scholarly literature.The notion behind the lunar effect has fascinated many behavioralists and warranted many experiments and studies. Most experiments, however, have found no correlation between the variables and, thus, refuted the theory.There are some studies which have results the researchers claimed supported the theory. For example, a study concluded that schizophrenic patients show signs of deterioration, in terms of quality of life and mental well-being, during the time of a full moon. Some researchers have claimed that there were strong positive correlations between physiological changes such as induced seizures in epileptic and non-epileptic people and the full moon period in studies they conducted. One study concluded that a statistically significant correlations for gastrointestinal bleeding among males in particular during this time. However, most of these findings are based on small-scale research.
On the other hand, the majority of scientific research seems to refute the theory of the lunar effect. Psychologist Ivan Kelly of the University of Saskatchewan (with James Rotton and Roger Culver) did a meta-analysis of thirty-seven studies that examined relationships between the moon’s four phases and human behavior. The meta-analysis revealed no correlation. They also checked twenty-three studies that had claimed to show correlation, and nearly half of these contained at least one statistical error. Kelly, Ronnie Martins, and Donald Saklofske evaluated twenty-one studies of births related to the phase of the moon and found no correlation. The scientific data “supports the view that there is no causal relationship between lunar phenomena and human behavior”. (Diefendorf 2007:113)A study of 4,190 suicides in Sacramento County over a 58-year period showed no correlation to the phase of the moon.
A 1992 paper by Martens, Kelly, and Saklofske reviewed 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. Psychologist Arnold Lieber of the University of Miami reported a correlation of homicides in Dade County to moon phase, but later analysis of the data — including that by astronomer George Abell — did not support Lieber’s conclusions. Kelly, Rotton, and Culver point out that Lieber and Carolyn Sherin used inappropriate and misleading statistical procedures.
When more appropriate tests were done, no correlation between homicides and the phase of the moon was found.Astronomer Daniel Caton analyzed 70,000,000 birth records from the National Center for Health Statistics, and no correlation between births and moon phase was found. Kelly, Rotton, and Culver report that Caton examined 45,000,000 births and found a weak peak around the third quarter phase of the Moon, while the full moon and new moon phases had an average or slightly below average birth rate.In 1959 Walter and Abraham Menaker reported that a study of over 510,000 births in New York City showed a 1 percent increase in births in the two weeks after full moon.
In 1967 Walter Menaker studied another 500,000 births in New York City, and this time he found a 1 percent increase in births in the two-week period centered on the full moon. In 1973 M. Osley, D. Summerville, and L. B. Borst studied another 500,000 births in New York City, and they reported a 1 percent increase in births before the full moon. In 1957 Rippmann analyzed 9,551 births in Danville, PA and found no correlation between the birth rate and the phase of the moon.A fifteen month study in Jacksonville, Florida also revealed at least no lunar effect on crime and hospital room admittance. In particular:There was no increase in crime on full moons, according to a statistical analysis by the Jacksonville Police Department. Five of the fifteen full moons had a higher than average rate of crime while ten full moons had a lower than average rate.
The higher-than-average days were during warmer months. Statistical analysis of visits to Shands Hospital emergency room showed no full moon effect. Emergency room admissions consistently have more to do with the day of the week.The word “menstruation” is etymologically related to “moon”. The terms “menstruation” and “menses” are derived from the Latin mensis (month), which in turn relates to the Greek mene (moon) and to the roots of the English words month and moon—reflecting the fact that the moon also takes close to 28 days to revolve around the Earth (actually 27.32 days). The synodical lunar month, the period between two new moons (or full moons), is 29.53 days long. Some authors believe women in traditional societies without nightlighting ovulated with the full moon and menstruated with the new moon.
A few studies in both humans and animals have found that artificial light at night does influence the menstrual cycle in humans and the estrus cycle in mice (cycles are more regular in the absence of artificial light at night), though none have demonstrated the synchronization of women’s menstrual cycles with the lunar cycle. One author has suggested that sensitivity of women’s cycles to nightlighting is caused by nutritional deficiencies of certain vitamins and minerals. Other animals’ menstrual cycles may be greatly different from lunar cycles: while the average cycle length in orangutans is the same as in humans—28 days—the average for chimpanzees is 35 days. Some take this as evidence that the average length of humans’ cycle is most likely a coincidence.