A hundred times NO – the moon does not cause a crazy night at the hospital

Yet another analysis has come out to kill the idea that hospital admissions and human birth rates are greater during the full moon than at other times. More than one analysis of such data shows conclusively that the moon has no correlation with these conditions. But, it’s such a widespread belief, I’m not sure another study will matter. A UCLA astronomer has published the piece in the journal Nursing Research.

Stop blaming the moon, says UCLA scientist | UCLA.

“It must be a full moon” is a common refrain when things appear more hectic than usual.

The moon is even blamed when things get crazy at hospital emergency rooms or birth wards. “Some nurses ascribe the apparent chaos to the moon, but dozens of studies show that the belief is unfounded,” said Jean-Luc Margot, a UCLA professor of planetary astronomy.

Of course, the moon does not influence the timing of human births or hospital admissions, according to new research by Margot that confirms what scientists have known for decades. The study illustrates how intelligent and otherwise reasonable people develop strong beliefs that, to put it politely, are not aligned with reality.

The moon is also ERRONEOUS correlated to all sorts of events such as increased rates of accidents, violent behavior, and criminal activity as well as outcomes for surgery and treatments, menstruation and depression. The belief is strongly ingrained in culture but the data is CONCLUSIVE. There is no controversy here. Margot found that a 2004 study in a nursing journal that suggested that the full moon influenced the number of hospital admissions in Spain was flawed in multiple ways and that there was no relation to the lunar cycle.

His paper is available here.

Roman, Soriano, Fuentes, Galvez, and Fernandez (2004) suggested that the number of hospital admissions related to gastrointestinal bleeding was somehow influenced by the phases of the Earth’s moon. Specifically, the authors claimed that the rate of hospital admissions to their bleeding unit is higher during the full moon than at other times. Their report contains a number of methodological and statistical flaws that invalidate their conclusions. Reanalysis of their data with proper procedures shows no evidence that the full moon influences the rate of hospital admissions, a result that is consistent with numerous peer-reviewed studies and meta-analyses. A review of the literature shows that birth rates are also uncorrelated to lunar phases.

Margot feels it’s imperative that we squash bogus beliefs because they can cause harm. We should be making decisions based on reality, not myths.

While I sought to dispel myths about the moon, I was also motivated by the fact that questionable beliefs are at the root of many of society’s worst problems. Could the lessons learned about flawed beliefs related to the moon be applied to a broader context?

He noted all the things that were wrong with the 2004 study including basic problems with the authors’ understanding of the lunar cycle so that the data collection procedure biased the results. The authors also missed an important consideration regarding days of the week. There were also problems with statistical tests that revealed the effect was too small and could be accounted for by other factors besides the lunar cycle.

There is no physical mechanism for a full moon effect – the moon is not closer, a gravity difference is not at play, people are not large water bodies like oceans that can be affected by the moon’s pull. And there are no electromagnetic or other crazy rays that radiate from the full moon during this time either. But confirmation bias is a strong factor in what people remember. The 2004 study proposed the lunar tides’ effect on blood as a possible explanation. This does not even work out mathematically and is clearly shown to be false. So, the paper was really a terrible study. Unfortunately, Margot had a hard time finding a publisher to rebut the bad study which is still out there misinforming health professionals.

When people off-handedly make such a comment “Must be a full moon!” you can be the stereotypical skeptic, check your phone app, and tell them, “Nope, waning gibbous”. That’ll show em’. But, seriously, it is important to point out in some way that believing in nonsense may seem harmless but it can be applied to other situations that we can’t foresee that can be detrimental to society.

Required reading: The Moon Was Full and Nothing Happened – CSI.

  28 comments for “A hundred times NO – the moon does not cause a crazy night at the hospital

  1. Peter Olausson
    March 31, 2015 at 11:46 AM

    There isn’t, but maybe there has been.

    Charles Raison has made a suggestion. Before artificial light, people used natural light as much as they could. A full moon on a cloudless sky meant they could stay up much longer. The sleep deprivation could trigger all kinds of disorders and erratic behavior. This could explain why “lunacy” is such a widespread notion; it was with us, sort of, for a very long time and everywhere.


  2. nite
    March 31, 2015 at 11:53 AM

    I work in public health with emergency department statistics, and I can verify this article is correct. A periodic wave as regular as the moon cycle would easily show up in every graph of every researcher and would be well known if there was any such thing.

  3. nite
    March 31, 2015 at 11:54 AM

    However, I cannot verify the statement “people are not large water bodies like oceans”. 🙂

  4. Old Muley
    March 31, 2015 at 12:12 PM

    At the elementary school that I work at, we keep daily records of the behavior of all our students. Since I had 3 years of data, and many teachers believe in the full moon effect, I decided to put it to the test. The result? A correlation of r=.03; about as close to nothing as you can get.

  5. Blargh
    March 31, 2015 at 12:16 PM

    Years ago, in a discussion about this myth, somebody brought up an interesting argument: that full moons could well have caused crazier than usual nights once upon a time, before the advent of cheap and ubiquitous artificial lighting (in the same way that street lights might actually increase crime).

    I don’t know if the myth goes back that far, though.

  6. ApexDisorder
    March 31, 2015 at 12:40 PM

    This subject has always pissed me off.
    Its just the earths friggin shadow, or lack of that one can see the phases of the moon.

  7. Blargh
    March 31, 2015 at 12:45 PM

    Its just the earths friggin shadow, or lack of that one can see the phases of the moon.

    The Earth’s shadow causes lunar eclipses. Ordinary lunar phases are caused by the moon orbiting the Earth and being lit from different sides. 🙂

  8. ApexDisorder
    March 31, 2015 at 1:20 PM

    Is the shadow on th moon caused by the earth?

  9. ApexDisorder
    March 31, 2015 at 1:38 PM


    This should clarify my point.
    Or perhaps I’m not on the same page as everyone else.
    Im open to critique.

  10. Lagaya1
    March 31, 2015 at 1:41 PM

    No, no, no. That would be an eclipse.

  11. Lagaya1
    March 31, 2015 at 3:22 PM

    It’s hard to illustrate in 2D pictures, so I always think of it this way: The moon is ALWAYS full. Whenever you see only half of it, you’re seeing half the dark side and half the full side. To see the entire full side, you would have to go out into space.

    It’s like taking a photo in a dark room with only one bright light. If the light is behind the subject, you get only a sillouette (new moon). If you are standing at the same angle as the light you get a full lighting. If you stand in the same angle but blocking the light, you get an eclipse. Move the light 10 feet to your right, and even though the subject of the photo is fully lit, you only see part of it lit because of your angle to it.

  12. ApexDisorder
    March 31, 2015 at 3:41 PM

    Very simple question.
    is the shadow on the moon created by the earth or not.
    If so I am correct, if not I am wrong.
    I hate mental gymnastics.

  13. CLamb
    March 31, 2015 at 3:54 PM

    The only time there is a shadow on the moon from the earth is during a lunar eclipse. The reason part of the moon is dark during normal lunar phases is that it is being shadowed by the part facing the sun.

  14. Blargh
    March 31, 2015 at 4:09 PM

    No, the Earth’s shadow doesn’t enter into it. It’s the moon’s own shadow. Shine a flashlight on a ball (or an orange, or whatever you have handy) – one side will be lit, one side will be in shadow.

    The tricky part is that the moon orbits the Earth with the same side facing us the entire time (a phenomenon known as “tidal lock”). So while we see the same side of the moon no matter where it is in its orbit, which side is facing the sun changes as it orbits.

    If the sun is on the other side of the Earth from the moon, you have a full moon, as the side facing us will be fully lit. When it’s 90 degrees off to the side, you have a half moon, as half of the side we see will be lit and the other half will be in shadow.

    This animation from the Wikimedia Commons should hopefully make everything clear.

  15. March 31, 2015 at 5:00 PM

    Ironically, many of the folks who seem to have certainty about effects of full moon on hospital or emergency room admissions…are the very ones who work there. Of course this is based on a very small sample of just a few people, but I still remember sitting in a van going out to a desert hike in Saudi Arabia when the subject came up. I was seated in between a teaching physician (from Ohio State University no less) and a nurse from Indiana who hadn’t previously met, and got to listen to them assuring me that it was both of their personal experiences that hospitals got super-busy at full moon times.

    In addition, I heard this from an operating room nurse from California…but she was also convinced that it was her O.R. that removed Richard Gere’s gerbil.

  16. nite
    March 31, 2015 at 5:36 PM

    The plural of anecdote is not data.

  17. Z-one
    March 31, 2015 at 5:48 PM

    I hear people toss around the statement “must be a full moon” almost as often as “Mercury must be in retrograde”. They both indicate a level of intellectual laziness to me. The change of phases of our moon is one of the most beautiful and accessible astronomical shows we get to witness, but relatively few people take the time to observe it — let alone understand it.

    It does take a bit of “mental gymnastics” to visualize the movements of the sun, moon, Earth, and other local planets in anything more than a two-dimensional graphic. It’s well worth the effort, however, and can inspire a sense of wonder in our little neighborhood of the galaxy.

  18. Lagaya1
    March 31, 2015 at 6:01 PM

    I have never heard anyone say that Mercury must be in retrograde. I must travel in the wrong circles!

  19. ApexDisorder
    March 31, 2015 at 10:11 PM

    I get it now.
    I was wrong and I love being wrong.
    I should have done the orbital solar system as a kid for the science fair.
    Instead I did a tornado with fans and dry ice. I think it was something I saw on Mr wizard.

    Learning is not a crime.

  20. One Eyed Jack
    April 1, 2015 at 8:54 AM


    Phil Plait explains it well.

  21. Rich
    April 1, 2015 at 8:56 AM

    It certainly isn’t.

    I was, until very recently, very comfortable that I knew why there were tides. Then I realised I could only securely explain to myself why there was one tide – moon pulling up on the water, big lump of water going round the planet, got that. So I started looking at why there was a tide on the other side at the same time, and frankly I’m not entirely sure. I read basic explanations that didn’t go far enough, or answer my question in enough detail, and the more I looked the more I found apparently authoritative sources giving different explanations – the earth is pulled *away* from the ocean, and/or its some form of centrifugal force acting on the ocean. Or not. I’ve read through whole reams of forum conversations arguing the points back and forward. So now I’m not sure about something I took for granted I knew.

    I can see why people settle for some sort of ‘paranormal’ explanation or received wisdom that doesn’t require a lot of thought. It’s hard work, thinking, and it involves admitting you don’t understand something, in public, even something simple – like tides, for example. Once you’ve asked the question, though, it’s interesting.

  22. One Eyed Jack
    April 1, 2015 at 9:02 AM

    I can assure you from personal experience that working in the medical field does not reduce the number of people with fallacious beliefs. You would like to think that medical professionals are more scientifically inclined and logical, but they’re pretty much the same as people in all walks of life… a mixed bag.

  23. One Eyed Jack
    April 1, 2015 at 9:03 AM

    The real question is whether they are serious or not. Many people say it just for fun, with no actual belief that there is a connection.

  24. One Eyed Jack
    April 1, 2015 at 9:26 AM


    The second tide is caused by inertia. The Earth and Moon form an orbiting pair. The Moon does not orbit around the Earth with the Earth remaining static. The Earth and Moon orbit around a common center of mass known as a barycenter. The water on the side of the Earth opposite of the Moon is being thrown outward the same way you are thrown to the outside a merry-go-round. Because of center of the orbit (barycenter) is roughly 4600 km from the center of the Earth (towards the Moon), the side opposite the Moon is experiencing the strongest inertial force due to its longer moment arm (distance from the center).

    Gravity from the sun also affects tides, but the effect is smaller (less than half as strong as the Moon) due to the much larger distance. When taken together, the actual tides we see are a complex interaction of the Earth, Moon, and Sun. Very fun stuff to think about, IMO. 🙂

  25. Rich
    April 1, 2015 at 9:50 AM

    (I’m aware that this is very much off topic, so I apologise, but I’m grabbing this opportunity while it’s there.)

    I see, I see. So this barycentre is always between the Moon and the Earth, which is why the second tide is opposite (on the side of the Earth away from) the Moon? (Also: the explanations of the ‘opposite’ tide being caused by the *earth* being pulled away from the ocean and towards the moon aren’t right? I wondered why/if that would result in a tide the same height as the gravity acting on water alone.)

  26. Russian Skeptic
    April 1, 2015 at 11:06 AM

    There is an even more bizarre belief – that excessive menstrual bleeding is caused by full moon.

  27. April 1, 2015 at 11:11 AM

    In addition to putative scientific mindfulness, One Eyed Jack, there is the fact that they are supposedly trained observers. They observe, or think they observe certain incidences of activity in the emergency room. But, as we know, it’s really really hard — sometimes impossible — to convince someone that what they think they see, what they personally observe, may be subject to all sorts of observer bias.

    In fact, I continually amaze myself at how wrong I often am when I actually get to counting things that I was sure were “the other way around.”

  28. Tallguy72
    April 1, 2015 at 7:08 PM

    Interesting how Margot had a “hard time finding a publisher” to rebut the study. I am wondering why that is? I have several ideas but am interested in hearing opinions.

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