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Moonstruck! Does The Full Moon Influence Behavior?

It happens at least once every month. Sometimes, rarely, it happens twice a month. Up there in the sky. It's a bird. It's a plane. No, it's a FULL MOON.
 
Popular legend has it that the full moon brings out the worst in people: more violence, more suicides, more accidents, more aggression. The influence of the moon and behavior has been called "The Lunar Effect" or "The Transylvania Effect." The belief that the full moon causes mental disorders and strange behavior was widespread throughout Europe in the middle ages. Even the word "lunacy" meaning "insanity" comes from the Latin word for "moon."
You may hear people
"Just ask an emergency room nurse or a police phone operator. They will tell you that they are busier on nights when there is a full moon."
Is there scientific evidence to support these beliefs? Let's look at the data.

Violence, Aggression and Crime
  • 11,613 cases of aggravated assault in a 5-year period: assaults occurred more often around the full moon.
  • 34,318 crimes in a 1-year period: crimes occurred more frequently during the full moon.
  • 58,527 police arrests in a 7-year period: no difference in the number of arrests made during any phase of the moon.
  • 361,580 calls for police assistance in a 3-year period: no relationship to the phase of the moon when day of the week, holiday and year were controlled.
  • 1,289 aggressive "incidents" by hospitalized psychiatric patients in a 105-week period: no significant relationship between the severity or amount of violence/aggression and phase of the moon.
  • The rate of agitation in 24 nursing home residents in a 3-month period: no significant relationship to moon phase.

Anxiety, Depression and Psychosis
  • The records of 782 patients and 4,600 consultations in an 18-year period: no relationship between the phase of the moon and the number of times people contacted their doctors for anxiety or depression.
  • The admission records of 18,495 patients to a psychiatric hospital in an 11-year period: admissions for psychosis were highest during the new moon and lowest during the full moon.
  • 25,568 psychiatric emergency room visits in a 13-year period: visits increased near the first quarter moon and a decreased around the new moon and full moon.

Suicides
  • 928 suicides in a 4-year period: suicides did not increase during the full moon. In fact, more suicides were noted during the new moon.
  • 897 suicides committed in a 3-year period: no relationship to the phase of the moon.
  • 504 suicides committed in a 1-year period: no relationship to the full moon.
  • 383 cases of attempted suicide in a 1-year period: no relationship to phase of the moon.
  • 1,997 suicides in a 13-year period: suicides did not occur more often during the full moon.
  • 4,190 suicides in a 58-year period: suicides had no relationship to the phase of the moon.
  • 1,187 cases of "self-poisonings" in a 1-year period: no relationship to the phase of the moon.
  • 841 cases of "self-poisonings" in a 4-year period: self-poisonings did occur more often on the day of the full moon.

Emergency Room Calls/Emergency Room Visits/Hospital Admissions
  • Calls to a poison center monitored over a 1-year period: unintentional poisonings occurred more often during the full moon cycle. However, the number of calls due to intentional poison exposure (suicides/drug abuse) was significantly LOWER during the full moon and higher during the new moon.
  • 1,444 trauma victim hospital admissions in a 1-year period: no increase during full moon.
  • 3,468 emergency room visits and hospital admissions by people who intentionally took poison: visits and admissions were not different on days with full moons.
  • 7,844 emergency calls to a suicide prevention/crisis call center in a 2-year period: the highest number of total calls was during the new moon, not the full moon. When calls for suicide threats were analyzed, there were more calls during the first quarter of the moon and new moon.
  • 36,268 calls to a crisis center in a 8-year period: no relationship to moon phase.
  • 736 telephone counseling calls in a 4-month period: no relationship to moon phase.
  • 100 admissions to a psychiatric hospital in a 3-year period: no relationship to the cycle of the moon.

Drug Use/Overdose
  • 1,182 drug overdose cases recorded in a 15-month period: no relationship to the full moon phase.
  • 949 cases of drug use (toxicology screenings) in a 1-year period: no relationship to the phase of the moon.

Accidents
 
  • 246,926 traffic accidents involving property damage and 50,492 traffic accidents with non-fatal injuries in a 9-year period: no relationship was found between accidents and moon phase. However, this research did find that accidents of both kinds occurred more often on Friday and Saturday and on Halloween. New Year’s Eve and Thanksgiving also had higher rates of traffic accidents involving property damage.
  • 2,382 fatal traffic accidents in a 13-year period: accidents were not higher during the full moon.
  • 4,835 traffic accidents in a 4-year period: no relationship to the phase of the moon. However, there was an increase in the number of accidents that occurred in the summer and on weekends.
  • Medical staff "incidents" recorded in a 4-year period: no relationship to the phase of the moon.

Problems Studying the Lunar Effect
Perhaps one of the first things that you notice about these studies is that the results are inconsistent. Some studies show that a particular behavior will occur more often during the full moon and other studies show no relationship between behavior and the full moon. This finding alone casts doubt on the theory that the full moon influences behavior. It may also be that experiments have been designed differently. For example, some studies include "full moon" behaviors that occur a few days before and after the full moon, while other studies include only those behaviors within a single day of the full moon.

Selective Memory?

Because many people believe that the full moon can affect behavior, experiments must be designed carefully to eliminate the possibility that people's beliefs will influence the data. For example, if people know that they are in an experiment which studies how the moon affects behavior, they may act in ways that change the results. It is possible that people have a "selective memory" for strange events that happen on the full moon; they remember strange incidents that occur during a full moon, but forget when these same things happen at other times.

Correlation Does NOT Mean Causation
 
It is also important to remember that studies that examine relationships between behavior and the phase of the moon determine only correlations. These types of studies determine if one set of numbers varies in a reliable manner with another set of numbers. If they do, then it can be said that a relationship exists.
 
The existence of a relationship between two "variables" DOES NOT mean that one variable causes the other variable. For example, if you looked for a relationship between the number of points scored by a basketball team and the number of books checked out of a library on different days, you might find a significant relationship. This doesn't mean that the score of basketball games causes people to check out library books or that checking out library books causes the basketball team to score more points. The reason why these two activities vary in a similar fashion is completely unknown and untested. It just happens that the two measurements vary in a related fashion.
 
In the basketball/library book example, the relationship could be caused by many things, maybe even by the weather. Maybe there was a lot of rain when the basketball scores and library books were counted. Perhaps the rain caused the basketball players to practice more (resulting in more points scored) and caused more people to visit the library (resulting in more checked-out books).
 
Some experiments do show that on days with a full moon there is more abnormal behavior. However, many of these studies have been criticized because they were not performed properly. For example, some of these experiments:
  • tested only a few people over a short period of time.
  • did not analyze the data with proper statistical tests.
  • did not take into account the day of the week on which the full moon occurred
  • did not take into account whether the full moon occurred on a holiday or a weekend.

Did you know?
The full moon appears once every 29.53 days.
The distance between the moon and the earth varies from about 221,463 miles (356,334 kilometers) to 251,968 miles (405,503 kilometers).
 
The diameter of the moon is 2,159 miles (3,475 kilometers). For comparison, the diameter of the Earth is 7,926 miles (12,756 kilometers).
 
The circumference of the moon is 6,790 miles (10,864 kilometers). For comparison, the circumference of the Earth at the equator is 24,902 miles (40,075 kilometers).
 
Sometimes there are two full moons in one month. It IS possible to have a month without a full moon, but this does not happen very often and it can happen only in the month of February. You will have to wait until February 2066 for the next month without a full moon.

Information supplied by http://www.faculty.washington.edu