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. The notion behind the lunar effect has fascinated many behavioralists and warranted many experiments and studies. 

Across the world, there has been an abundance of pseudoscientific theories and superstitions based on this premise. One theory claiming that the moon has a perceived relationship to fertility is due to the corresponding human menstrual cycle, which averages 28 days. However, only about 30 percent of women have a cycle length within two days of the average. Furthermore, the cycle of lunar phases is 29.53 days long, so the cycles would soon get out of synchronization. Some say that upon seeing the new moon you should hand over whatever silver you have in your pockets or handbag, which supposedly ensures prosperity for the following month.

According to some traditions, prior to the advent of modern techniques, surgeons would supposedly refuse to operate on the full moon because of the increased risk of death of the patient through blood loss. As with most folklore and urban legends, the notion behind the lunar effect has also found its way into the news. For example, most recently, it has been alleged that the full moon may have influenced voter behavior in the US 2000 presidential election.

In the UK, a survey has found that car accidents rise by up to 50 percent during full moons. 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. 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.

Most experiments, however, have found no correlation between the variables and, thus, refuted the theory of lunar effect. Over the past 30 years, even more evidence has emerged to stress that it is pseudoscience.

The majority of scientific research seems to refute the theory of the lunar effect. Psychologist Ivan Kelly of the University of Saskatchewan 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. 

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 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.

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. In 1959 Walter 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 he 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.

A fifteen month study in Jacksonville, Florida also revealed no lunar effect on crime and hospital room admittance. 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.