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.

你可能曾在电影中看到：月圆时分，一个男人变成毛茸茸的骇人怪物在城市里四处横行，把人撕成碎片。你也许对狼人的故事感到好笑，但你可曾好奇过满月与疯狂举动之间的联系从何而来？

这种观念在恐怖电影出现之前便已流传许久。“lunacy”这个表示“疯狂”的词源自“Luna ”一罗马神话中月光女神的拉丁名。一百年前，欧洲的一些医院在月圆时因为担心会出现暴力行为， 而用链子绑住那些被认为是疯子的患者。

令人惊讶的是现在仍有很多人相信月亮会让人行为失常。例如，许多医务工作者相信月圆时急诊病例会增多。很多研究工作已着手进行以建立月亮圆缺与人类和其它动物生物钟之间的联系，而且得到了各种不同的结果。

美国一项研究发现人们在满月时饮酒量减少而食量增加。意大利研究人员发现，月圆后的一两天内，婴儿的出生人数较多。而英国最大的电讯公司则宣称，在月圆的前7天，网络使用率会增加。

然而其他研究人员发现，某些宣称能证明月圆与人类行为有关的研究存在方法上的严重错误。而且没有一项研究发现月亮圆缺与人类忧郁症或颠狂症的发作有直接联系。

只有微弱的科学证据能证明疯狂举动与月亮有关，也许解释这个说法存在的最好方法是把它当作一种过去的遗俗。在发明电之前很长一段时间，皎洁的月光会诱发特别的夜间活动。对一些人来说，即使只是一晚不睡，也足以让他们发狂──不管他们手上有没有长毛。