This week, a news story based on a scientific study announced that researchers found evidence that the full moon affects our sleep. The results were published widely because, I believe, it reinforces our thinking that the moon is magical and influential.
We like to be right and to have our prior beliefs bolstered. Once again, your friendly neighborhood skeptic is here to suggest don't be so hasty. There is more to this than "full moon fever."
Everyone knows that the full moon makes people looney right? Luna, Latin for moon, is the root of the word lunatic. Emergency rooms and police stations are crazy during full moon nights. Right?
Wrong. Much is mistaken about these folk beliefs.
It's likely you will completely reject what follows out of hand because it does not reinforce your prior beliefs, it demolishes them. We humans hate when that happens so we cling to the belief and attempt to justify it. But here goes, have a listen.
Study after study have shown the there is no increase in episodes of madness, disasters, traffic accidents, emergency calls, assassinations, violent crime, sleepwalking, births, suicides, homicides, arson, epilepsy, or werewolf sightings associated with the moon phases. Occasionally, one study may show a small effect but when reasonable controls are applied to the data, the effect disappears. The corrections include allowances for days of the week, weather, or other factors that could influence certain events (for example, car accidents or violent altercations) to happen more often. Also, we have to watch how events are recorded or counted and if they occur exactly at a full moon or how far ahead or behind of the moon phase. When we account for all these real-world complexities (or attempt to account for them all), we find that the lunar effect disappears.
Yet, long ago, lunacy laws were on the books in England. A lawyer representing a client could claim a defense of moon madness and be off the hook for temporary insanity. We don't have such laws anymore because that's nonsense.
I know what you are going to say... gravity and tides. The moon clearly affects the tides on earth and since the human body is mostly water, the moon affects us, too. Well, I don't see people bulging with water according to the moon phases like the earth does. If we were really this sensitive, this effect from the moon would be clearly noticable and we wouldn't be having this discussion. The moon's gravity affects the Earth because the moon and Earth are both big and near each other. The strength of the tidal force is associated with the alignment of the sun, Earth and moon, not the phase of the moon that we notice here on the ground because of reflected sunlight. Each of us as individuals are small and far away from the moon. Researchers Rotton and Kelly calculated that at birth, a 55 kg mother holding her baby exerts 12 million times more tidal force on the child than the moon because she is close and comparatively big. Each person on Earth is affected by the moon's gravity a negligible amount. [Source: Kelly, I. W., James Rotton, and Roger Culver. "The moon was full and nothing happened." Skeptical Inquirer 11 (1985): 129-133.]
Is there some other force from the moon that affects us? Yes. Culture. Culture is a huge force that has a deep and lasting influence on us for our whole lives - as long as we spend time with other people. Literature, movies, television, news, and folklore all contribute to the idea that the moon is something special. It's gorgeous, and it DOES affect organisms and processes on earth. But there is no evidence that it directly affects human behaviors - with one caveat - and it's a BIG one - cognitive bias. When we see the full moon, we attribute weird events to it thanks to the pop culture associations. Like moon madness, some people still use it as an excuse to act out. That does not mean the moon is the cause. Peoples' perception about the moon are the cause. There is no physical property about the moon that we know of to affect our puny human bodies (and we can measure REALLY small effects).
So what do we make of the sleep study mentioned this week? There are some issues with it that should make us pause. Participants in the study were being observed for other reasons. The moon phases were applied to the data set AFTER it was completed. They had trouble falling asleep and sleeping as long when the moon phase was full. That must mean something! It might. Yet, one study does not overturn dozens of others that showed no effect unless it was a particularly rigorous and impressive study. We can't really say that about this one. It followed only 33 people. The results could have missed some factor. It would need to be repeated to see if the conclusions stand. Besides, the effect was small. Slight trouble sleeping is not comparable to more extreme behaviors related to "lunacy". Perhaps this moon-sleep effect is a remnant of our ancestral internal clock. At most, it suggests that perhaps in the past, when we were more in tune with natural signals, the moon phase was an integral part of schedule. It's not as prevalent now and can not be used as justification for other behaviors.
I expect this study might be cited the next time people claiming lunar effects ruined their evening and I just roll my eyes. How often do you hear "Oh, it MUST be a full moon!" Does anyone actually check? Do you remember when it isn't a full moon? What's the excuse for a busy night at the emergency room during a waning phase? There are many and various explanations for a crazy evening. The moon is not a valid one.
The next time you can't sleep, it may be because there is a bright full moon shining into your room like a celestial nightlight. You walk to window to look at it. It's big and beautiful, you are moonstruck and up come memories and myths that we have internalized about the Earth's satellite. What it doesn't do is make you "mad."