Across the centuries, many a person has uttered the phrase “There must be a full moon out there” in an attempt to explain weird happenings at night. Indeed, the Roman goddess of the moon bore a name that remains familiar to us today: Luna, prefix of the word “lunatic.” Greek philosopher Aristotle and Roman historian Pliny the Elder suggested that the brain was the “moistest” organ in the body and thereby most susceptible to the pernicious influences of the moon, which triggers the tides. Belief in the “lunar lunacy effect,” or “Transylvania effect,” as it is sometimes called, persisted in Europe through the Middle Ages, when humans were widely reputed to transform into werewolves or vampires during a full moon.

The full moon has been associated with strange or insane behaviour, including suicide, sleepwalking and violence. … Many people dismiss myths concerning the influence of the moon, but real effects are being found through science. Lunacy is linked to the moon. Lunacy and lunatic stem from the word luna, the Latin word for moon.

Even today many people think the mystical powers of the full moon induce erratic behaviors, psychiatric hospital admissions, suicides, homicides, emergency room calls, traffic accidents, and all manner of strange events.

Following Aristotle and Pliny the Elder, some contemporary authors, such as Miami psychiatrist Arnold Lieber, have conjectured that the full moon’s supposed effects on behavior arise from its influence on water. The human body, after all, is about 80 percent water, so perhaps the moon works its mischievous magic by somehow disrupting the alignment of water molecules in the nervous system. Though this makes perfect sense in its own way, there are more reasons against this theory than to support it.

So if the lunar lunacy effect is merely an astronomical and psychological urban legend, why is it so widespread? There are several probable reasons. Media coverage almost surely plays a role. Many Hollywood horror movies portray a full moon at peak times of spooky or deadly occurrences.

A good  reason for the proposed mystery and superstitions of the full moon could well simply be the human mind’s tendancy to remember events by relating them to memorable happenings at the time therefore ‘It happened during a full moon’ is more likely to be remembered than ‘it happened a week last Tuesday’…

Has anyone any opinions on this?