Effects of the Lunar Phases
Does a Full Moon Influence
Human Behavior?

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". 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." Is there scientific evidence to support these beliefs? Let's look at the data.

Human Agression & the Lunar Cycle
Full Moon Fun
Can the Moon Cause Earthquakes?
The Moon & Madness
How the Moon Affects You!
Scientists Shed Light On Full Moon Myths
Lunar Influence & Emergencies
Lunar Cycles & Accidents
Are People More Active During A Full Moon?
The Full Moon & Traffic Accidents
Lunar Cycles & Violent Behavior
Moon Cycle & Behavior : Myth or Fact?
Can The Full Moon Affect Behavior?

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.