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January 12, February 10, and March 12 are the first full moons of the year. You’ve probably heard other nurses comment that during the full moon, things go a little crazy. There’s a persistent belief that ERs get busier and there are more injuries, more childbirths, and other changes during the full moon. While anecdotal evidence and personal experience may make it seem like the “lunar effect” is a real thing, that’s probably not the case. Most of the evidence at hand suggests that the lunar effect is simply a myth, stemming from widespread archetypal and cultural symbolism and ideas surrounding the full moon.
Debunking the Lunar Effect
There have actually been numerous studies looking for a potential causal relationship between the phase of the moon and the incidence of injuries and trauma. Nearly every study has suggested that the idea is statistically unfounded, and that no link between injuries and the full moon can be identified.
In one early 1989 study, researchers found no statistical difference between the number of ER admissions during the full moon and during other times. The was also no difference in mortality rate, injury severity score, or mean length of stay. A later 2004 study reported similar findings. A 1992 study found no link between moon phase and crisis calls.
So if every single study exploring the idea of the lunar effect has found no causal relationships between the full moon and medical problems, why do people still believe in it? Where did this idea come from?
The Sleep Deprivation Hypothesis
Some researchers hypothesize that the belief in a relationship between madness and the full moon may stem from sleep deprivation. In pre-modern societies, the moon was the primary source of light at night. During the full moon, the night sky would be much brighter. It’s possible that before the invention of electric lighting, the bright light from the full moon would make people more susceptible to sleep deprivation. Sleep deprivation can trigger mania in people with manic depressive disorder. It can also trigger seizures in people with epilepsy.
It’s possible that in the past, the full moon really did have an effect on people’s behavior, because it made them more likely to be sleep deprived. It can’t be known for sure, but this might be part of the origin of the myth of the moon and madness.
Unraveling an Ancient Myth: How Sleep Deprivation Affects Mental Illness
There is a traditional association, at least in Western culture, between the full moon and “madness” — that is, unusual behavior or mental illness. If it is true that the full moon’s bright light made people more susceptible to sleep deprivation, it’s possible that in pre-industrial times, people with conditions like bipolar disorder were more likely to suffer manic episodes around the time of the full moon. Bipolar disorder was not particularly well understood until the 20th century, and it was only in the 1970s that its subtypes were added into the DSM.
Bipolar disorder and sleep disturbances are known to coexist in patients. Plus, sleep deprivation can affect different individuals with the disorder differently. At least one functional polymorphism has been identified, affecting 5-hydroxytryptamine transporter (5HTT) coding sequences. This has been linked to differences in the effects of sleep deprivation on the mood disorder symptoms of different people with bipolar disorder.
There has also been at least one study looking for links between the full moon and violent behavior in schizophrenic patients. However, no significant link was found.
Moon and Myth
Since the dawn of cognitive and behavioral modernity, the moon has had a significant presence in the myths and consciousness of humans around the world. People were quick to notice its cyclic waxing and waning, and they looked upon it in wonder and awe.
The moon has many effects on our planet, and without it, there might not have ever been biological life on Earth. But physiologically, it does not have any effects on human behavior, with or without the presence of mental illness. It doesn’t make people more violent, more unstable, or any more likely to be injured. If it ever did, it would have been due to sleep deprivation from its bright light, not from any effects of the moon itself.
Although the myth of the lunar effect persists among nurses and other medical professionals, no research has ever established a causal link between the moon and madness or medical problems.
