Since time immemorial, man has linked full moon to man’s insanity. This link is what is more popularly known as “lunacy.” The belief as regards lunacy is rooted in folklore and not on any scientific study or evidence. "Lunacy" is named after the moon (luna). The occurrence of full moon is often linked to mental illness or mental disorder. Though there are numerous studies which have tried to find the effects of full moon, these studies have failed to establish its relation with human behavior. There have been many studies conducted by the different experts, such as Ivan Kelly, James Rotton and Roger Culver regarding lunar effects and they concluded that the studies did not show any reliable and significant correlation between the full moon or any other phase of the moon and the psychological behavior of persons.

          Though there are studies which prove that there is no relation between full moon and the psychological behavior of humans, people still believe thay a relation exists. Kelly, Rotton, and Culver explain that there are four factors which greatly contribute to this belief. These are media effects, folklore and tradition, misconceptions, and cognitive biases. A fifth factor may be considered, and that is, communal reinforcement.

          One major factor for the wrong belief regarding lunacy is the moon's effect on tides. This belief has greatly contributed to lunar mythology. Many people think that since the moon affects the ocean's tides, such effects are so powerful that it affects the human body as well, most particularly, human behavior. But actually, the lunar force is a very weak tidal force. According to Astronomer George O. Abell, a mosquito would exert more gravitational pull on your arm than the moon would. Moreover, a mother holding her child would exert 12 million times as much tidal force on her child as the moon.

          It s the fact that the human body comprises mostly of water that contributes to the notion or belief that the moon has a powerful effect on the human body hence, on one’s behavior. It must be realized that the moon only affects the unbounded bodies of water.The water in the human body is bounded..

          More so, the tidal force of the moon on the earth depends on its distance from earth and not its phase. Higher tides occur at new and full moons. However, these tides occur not because the moon's gravitational pull is stronger at those times, but rather, the tides are higher then because the sun, earth, and moon are in a line and hence, the tidal force of the sun joins the moon at those times to produce higher tides.

          Many believe in lunar myths because they have heard them repeated many times by members of the mass media, by police officers, nurses, doctors, social workers, and other people with influence. Once many people believe something and enjoy a significant amount of communal reinforcement, they get very selective about the type of data they pay attention to in the future. If one believes that during a full moon there is an increase in accidents, one will notice when accidents occur during a full moon, but be inattentive to the moon when accidents occur at other times. If something strange happens and there is a full moon at the time, a causal connection will be assumed. If something strange happens and there is no full moon, no connection is made, but the event is not seen as counterevidence to the belief in full moon causality. Memories get selective, and perhaps even distorted, to favor a full moon hypothesis. A tendency to do this over time strengthens one's belief in the relationship between the full moon and a host of unrelated effects. The most widely believed myth about the full moon is its association with madness. However, in a study conducted examining 100 studies, t was found out that the phases of the moon accounted for no more than 3/100 of 1 percent of the variability in activities usually termed lunacy. James Rotton says that such a small percentage is too close to zero to be of any theoretical, practical, or statistical interest or significance.

          The common notion of people that there is a lunar influence on suicide also appears to be unsubstantiated. Numerous studies conducted for nearly over three decades found no significant association between phases of the moon and suicide deaths, attempted suicides, or suicide threats. In 1997 a study of 897 suicide deaths in Madrid found no significant relationship between the synodic cycle and the suicide rate. These studies failed to find anything interesting happening during the full moon.

          In sum, it can be said that there is really no connection between lunacy and full moon. There is no statistical proof from any hospital or police records which prove that people are crazier, or that more crimes are committed, or that more babies are born when there is a full moon. The misconception arises from the condition that the moon to the casual observer appears to be full in the sky for a period of four or five days around the actual full moon. If there is really a psychological effect of full moon, perhaps the presence of similar occurrences happening during the new moon phase must be noted.

References:

http://www.astronomy.org/astronomy/misconceptions.html

Kelly, I.W., James Rotton, and Roger Culver. "The Moon was Full and Nothing Happened: A Review of           Studies on the Moon and Human Behavior and Human Belie.,"

Rotton, James. "Moonshine," Skeptical Inquirer, May/June 1997

http://skepdic.com/fullmoon.html