Full Moon Crazy?

Many people believe that the full moon correlates with a whole bunch of crazy and abnormal behavior. I used to hold this particular belief myself.

So does the full moon cause abnormal human behavior? Well. No.

The best studies on the subject find no increase in the types of behavior usually associated with the full moon during that time. Things like; Psychotic episodes, Emergency room admissions, emergency services call outs and so on.

This is an old belief that is firmly ingrained in the popular culture. The word “lunatic” derives from the Latin term luna, or moon. In 19th-century England, some lawyers used a “not guilty by reason of the full moon” defense to acquit clients of crimes committed during full moons. And yes, it actually worked on a number of occasions. One study revealed that up to 81% of mental health professionals believe in the lunar effect, and a study of nurses demonstrated that 69% believe that full moons are associated with increase in patient admissions.

The common reason given to explain the effect is that the human brain is mostly water. We know that the moon has an enormous effect on water on the earth because we observe it in the tides. So the logical inference is that the moon is affecting the human brain according to it's phase. There two major things wrong with this argument. First. The tidal effect of the moon is not related in any way to it's phase. The tidal effect of the moon is related to its position in its orbit and its distance form the earth (the orbit of the moon is not a circle). Second. The tidal forces exerted by the moon on a human are simply far to small. Tidal force is a result of the difference in gravitational force due to the moon from one side of the earth to the other. It is significant on the earth because one side of the earth is closer to the moon than the other by an amount that is significant relative to the distance between the two. And because the oceans are large and they all, you know, connect. for the same reason that we don't observe a tidal effect in a swimming pool. There can be no tidal effect due to the moon on the human body. In fact. A fly sitting your arm will exert a greater tidal effect on your brain than the moon!

So why is this belief so widely accepted?

Humans are programmed to remember events. We don't do so well with remembering non events. This is a form of confirmation bias. When someone has the idea that the full moon correlates with weird behavior. They will remember the times that this correlation holds true as an event and forget the times when there was strange behavior that didn't occur at the full moon. The latter is a non event. Remembering non events is not useful and a wasteful use of valuable memory so we have evolved not to do it. This is certainly how I came to believe in the full moon effect.

To summarize. There likely is no full moon effect. This is one of those a commonly held and accepted beliefs that happens to be false. This belief is most likely due to confirmation bias. By understanding confirmation bias and how it influences human reasoning. We can be on guard to ensure we don't fall into its carefully laid trap.