Claims of a lunar connection have appeared in the following contexts:
Fertility 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.
Birth rate Multiple studies have found no connection between
birth rate and lunar phases. A 1957 analysis of 9,551 births in
Danville, Pennsylvania, found no correlation between birth rate and the phase of the Moon. One team, in
Barcelona,
Spain, reported a weak correlation between lunar phase and hospital admissions due to
gastrointestinal bleeding, but only when comparing full Moon days to all non-full Moon days lumped together. The Spanish team acknowledged that the wide variation in the number of admissions throughout the lunar cycle limited the interpretation of the results. A spokesman for the
Royal College of Surgeons said they would "laugh their heads off" at the suggestion they could not operate on the full Moon.
Human behavior Epilepsy A study into epilepsy found a significant negative correlation between the mean number of epileptic seizures per day and the fraction of the Moon that is illuminated, but the effect resulted from the overall brightness of the night, rather than from the moon phase per se. This followed research by the
Sussex Police force that concluded there was a rise in violent crime when the Moon was full. A spokeswoman for the police force said "research carried out by us has shown a correlation between violent incidents and full moons". A police officer responsible for the research told the BBC that "From my experience of 19 years of being a police officer, undoubtedly on full moons we do seem to get people with sort of strange behavior – more fractious, argumentative." 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. A reported correlation between Moon phase and the number of homicides in
Miami-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. A 2009 study of over 23,000 aggravated assaults in Germany between 1999 and 2005 found no correlation with lunar phases. A 2016 study comparing indoor and outdoor crime in the
District of Columbia found that the intensity of moonlight had no effect on indoor crime, but a positive effect on outdoor criminal activity. The study's authors speculated that the effect may be due to criminals being better able to assess potential victims and unsecured properties, and there being more such victims out on the street on lighter nights.
Motorcycle fatalities A study of 13,029 motorcyclists killed in nighttime crashes found that there were 5.3% more fatalities on nights with a full moon compared to other nights. The authors speculate that the increase might be due to visual distractions created by the moon, especially when it is near the horizon and appears abruptly between trees, around turns, etc.
Stock market Several studies have argued that the stock market's average returns are much higher during the half of the month closest to the new moon than the half closest to the full moon. The reasons for this have not been studied, but the authors suggest this may be due to lunar influences on mood. Another study has found contradictory results and questioned these claims.
Meta-analyses 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. A study published in 2021 by researchers from the
University of Washington,
Yale University, and the
National University of Quilmes showed a correlation between lunar cycles and sleep cycles. During the days preceding a full moon, people went to bed later and slept for shorter periods (in some cases with differences of up to 90 minutes), even in locations with full access to electric light. Finally, a Swedish study including one-night at-home sleep recordings from 492 women and 360 men found that men whose sleep was recorded during nights in the waxing period of the lunar cycle exhibited lower sleep efficiency and increased time awake after sleep onset compared to men whose sleep was measured during nights in the waning period. In contrast, the sleep of women remained largely unaffected by the lunar cycle. These results were robust to adjustment for chronic sleep problems and obstructive sleep apnea severity. As for how the belief started in the first place, a 1999 study conjectures that the alleged connection of moon to lunacy might be a 'cultural fossil' from a time before the advent of outdoor lighting, when the bright light of the full moon might have induced sleep deprivation in people living outside, thereby triggering erratic behaviour in predisposed people with mental conditions such as bipolar disorder. ==Other organisms==