Why People believe that the Full Moon can Affect Behavior

Ever since ancient times, there has been a strong belief that full moon influences human behaviour. This influence is often referred to as ‘The lunar effect’ and has been used theoretically to explain the heightened aggression and manic behaviour displayed by some people with mental health problems.
For many years people with mental disorders were referred to as ‘lunatics’, a name that clearly identifies lunar influence as the cause of madness, mania and psychotic episodes. 

In “Lunacy and the Full Moon,” Scott O. Lilienfeld and Hal Arkowitz explain that it was the belief of philosophers, such as Aristotle and Pliny the Elder, that the brain could be affected by phases of the moon, because the brain is the softest human organ and is filled with fluid. Knowing that the tides are controlled by the phases of the moon, it seemed possible to those philosophers that the moon might have an equal pull on the liquid contained in a human brain.

Many folk tales about strange behavior during a full moon, and legends concerning men turning into werewolves at full moon, originated in Europe during the Middle Ages. Some of these myths have been perpetuated in modern horror stories, movies, dramas and novels.

Attitudes to mental illness

Paracelsus of Hohenheim, a revered alchemist and philosopher in the sixteenth century, was also a professor of physic, medicine and surgery. In his definition of mental illness he clearly stated that some patients suffering from mania were affected by phases of the moon. Although, as Franz Hartmann MD establishes in “Life of Paracelsus,” it was also his belief that some people would be inclined to lunacy if there had never been a moon.

The authorities in control of lunatic asylums in the eighteenth century firmly believed that mentally disturbed people became more violent around the time of a full moon. Inmates of the Bethlehem Hospital in London, the mental institution known as ‘Bedlam,’ were regularly flogged when a full moon was due. These floggings continued up until 1808 and were thought to prevent further outbreaks of violence amongst the mentally disturbed.

Possible reasons for the theories

One rational explanation for the origin of theories about the moon influencing human behaviour is provided by Senior Resident in Psychiatry Alina Iosif and Professor Bruce Ballon of the University of Toronto. They suggest in “Bad Moon Rising” that many people would have had less sleep around the time of a full moon, when moonlight can be very bright. Most people would have been able to sleep more during other phases of the moon. Iosif and Ballon explain that sleep deprivation can cause disturbed behavior in people who are predisposed to suffer from psychotic episodes.

Statistical evidence 

Although many people believe that more violent crimes, suicides and psychiatric disturbances occur during the full moon. No direct relationship to the phases of the moon can be detected from all the statistics that show no increase in crime, aggression or mental disturbances at the time of a full moon.

Despite the evidence that exists against theories that a full moon influences human behaviour, it is likely that many new books, movies and articles about the lunar effect will continue to appear. A full moon is always going to be regarded by some as a dangerous time. It is an idea based on perceptions that have been around for a very long time.