You have probably seen it in movies: When the moon is full, a man turns into a hairy, frightening creature and runs around the city, tearing people to pieces. You may laugh at stories of wolf men, but have you ever wondered where the association of a full moon with crazy goings-on came from?

Such notions have been around a lot longer than scary movies. The word lunacy, meaning "madness," is derived from Luna, the Latin name for the Roman goddess of the moon. And, a hundred years ago in some European hospitals, fear of violence during full moons led doctors to chain up patients thought to be lunatics.

It is surprising how many people still believe that the moon can affect human behavior in unusual ways. For example, many medical workers are convinced that the number of emergency cases increases during a full moon. Considerable research has been conducted to establish a link between the cycle of the moon and the biological clocks of humans and other animals, with varying results.

One study in the United States found that people drink less alcohol and eat more during a full moon. Italian researchers found that more babies seem to be born in the one or two days following a full moon. And Britain's largest telecommunications company claims that Internet use increases during the seven days before a full moon.

Other researchers, however, have found serious methodological flaws in some of the studies that claim to demonstrate a relationship between a full moon and human behavior. Also, no research has yet found a direct link between the phases of the moon and attacks of depression or mania.

With only weak scientific evidence relating madness to the moon, perhaps the best way to explain the existence of this myth is to call it a relic of the past: Long before electricity, bright moonlight was an invitation for extra nighttime activity. And for some people, even just one night without sleep is enough to induce mania in them—whether or not they have hair on their hands.

你可能曾在電影中看到：月圓時分，一個男人變成毛茸茸的駭人怪物在城市里四處橫行，把人撕成碎片。你也許對狼人的故事感到好笑，但你可曾好奇過滿月與瘋狂舉動之間的聯系從何而來？

這種觀念在恐怖電影出現之前便已流傳許久。“lunacy”這個表示“瘋狂”的詞源自“Luna ”一羅馬神話中月光女神的拉丁名。一百年前，歐洲的一些醫院在月圓時因為擔心會出現暴力行為， 而用鏈子綁住那些被認為是瘋子的患者。

令人驚訝的是現在仍有很多人相信月亮會讓人行為失常。例如，許多醫務工作者相信月圓時急診病例會增多。很多研究工作已著手進行以建立月亮圓缺與人類和其它動物生物鐘之間的聯系，而且得到了各種不同的結果。

美國一項研究發現人們在滿月時飲酒量減少而食量增加。意大利研究人員發現，月圓后的一兩天內，嬰兒的出生人數較多。而英國最大的電訊公司則宣稱，在月圓的前7天，網絡使用率會增加。

然而其他研究人員發現，某些宣稱能證明月圓與人類行為有關的研究存在方法上的嚴重錯誤。而且沒有一項研究發現月亮圓缺與人類憂郁癥或顛狂癥的發作有直接聯系。

只有微弱的科學證據能證明瘋狂舉動與月亮有關，也許解釋這個說法存在的最好方法是把它當作一種過去的遺俗。在發明電之前很長一段時間，皎潔的月光會誘發特別的夜間活動。對一些人來說，即使只是一晚不睡，也足以讓他們發狂──不管他們手上有沒有長毛。