Sections

Services

Information

UK United Kingdom

Monday’s medical myth: hospitals get busier on full moons

It’s another busy night in an inner city hospital emergency department (ED) and patients keep pouring in with injuries from accidents, assaults and self-harm attempts. One veteran nurse turns to a junior…

Studies into the lunar effect show no difference in rates of harm on full moons. Bill Gracey

It’s another busy night in an inner city hospital emergency department (ED) and patients keep pouring in with injuries from accidents, assaults and self-harm attempts. One veteran nurse turns to a junior doctor, rolls her eyes and mutters, “must be a full moon tonight.”

The junior doctor racks her sleep-deprived brain to remember what the moon looked like on the way to work. She can’t recall – and doesn’t bother checking – but files the incident away so she can bring it up at social gatherings and retell it as part of the folklore of the ED.

What we have just witnessed (or something like it) happens every week around the country. Despite the “lunar effect” being one of the most easily studied and thoroughly debunked myths in medicine, it provides a fascinating look at the psychology of rational people who work in jobs where superstitious beliefs can easily develop.

But first, the science.

The biggest study I can find debunking the myth is a 2004 paper from Iran. It analysed just under 55,000 trauma-related admissions to three EDs over 13 months. There was no difference between full-moon days and other days in the number of attendances, nor in the type or severity of patients treated.

Other well-conducted studies include this 1992 Canadian analysis of the relationship between crisis calls to police stations and poison centres, and the lunar cycle (there was no correlation). And this review, also from 1992, which found no relationship between full moons and increased suicide attempts.

Junior doctors from Sydney’s busy St Vincents Hospital emergency department. Foxtel

A less technical summary from Scientific American explains the ancient origins of the belief: the moon was thought to cause intermittent insanity. That’s why the latin word for moon, luna, forms the base of the out-dated term lunatic.

Perhaps more interesting in the Scientific America summary is that the myth persists within groups of professionals who deal with unpredictable patients, such as mental health professionals and emergency service personnel.

Two important effects are at work here. The first is confirmation bias. This is the innate tendency of people to remember and pay attention to facts that confirm an already-held belief, and ignore or downplay facts that tend not to support it.

There are many, many busy and stressful nights in ED and some of them inevitably fall on nights when the moon is full. These will be the ones that ED staff remember, and they will tend to forget the ones which are not on full moon nights.

The second likely cause of such a persistent myth is that those who work in fields that are inherently unpredictable – where stakes are high and conditions demanding – are more likely to be prone to superstitious or magical thinking. It is a form of the illusion of control cognitive bias.

Part of feeling able to cope with the randomness of life is to develop associations which can be given a meaning, even if the belief seems absurd. The psychologist Michael Shermer has coined the term “patternicity” to describe this tendency in the context of evolutionary psychology.

So despite a pedigree dating back to Aristotle, the belief that the full moon affects behaviour in any way only persists because of the very human responses of our front-line health personnel. When they’re feeling under the pump, they begin to instinctively look for patterns in random events.

Join the conversation

12 Comments sorted by

  1. Gary Campbell

    RN

    As a Registered Nurse who spent quite a bit of his career in the critical care areas (ICU, A&E, CCU) I can honestly say the "Full Moon" effect commences approximately two weeks before a full moon, and extends to two weeks after the full moon.

    report
    1. Grendelus Malleolus

      Senior Nerd

      In reply to Gary Campbell

      *grins* at the wit of the RN

      I was considering a thesis based on the effect of lunar cycles on police activities but only a very little amount of literature review, and a quick look at key crime statistics showed I was unlikely to find any link at all. What I did find was far more interesting - there are cycles of crime related to natural events, but entirely rational in explanation - less burglary when it rains for example.

      report
    2. jamie jardine

      Acupuncturist

      In reply to Grendelus Malleolus

      If you think about it in times gone past, before electric light a full moon would have meant a lot more people than normal would be out and about at night doing all sorts of things, not mention magical rituals and religous ceremonies, so there may have been some truth in this myth at one time.

      report
    3. Grendelus Malleolus

      Senior Nerd

      In reply to jamie jardine

      At a time before hospitals and Emergency rooms?

      Speculation that more things happened in the past unfortunately remains speculation unless we were able to find a journal of daily events. However my own view is that the potential increased activities that made use of additional light on full moon lights would be balanced by the activities on nights where there was some extra light from a gibbous moon in wax or wane, or in fact on moonless lights from the additional activities of people who wish not to be seen at all.

      None of which changes the measurable reality of today that the presence of the full moon in the sky does not actually influence behaviour.

      The one caveat I might add to that is that many amateur astronomers that I know get quite irritable around the time of the full moon as all that extra light pollution ruins their plans to observe some crucial event.

      report
    4. jamie jardine

      Acupuncturist

      In reply to Grendelus Malleolus

      I'm speaking generally, if you have ever lived in the country side away from the effects of the city lights then you understand the significance of a full moon. In particular I love riding my horse on a full moon, it's like the night becomes day, beautiful time to be out. So its not a far stretch to imagine heightened activity on a full moon in times past would have translated into more work for law enforcement and emergency care.

      report
    5. Grendelus Malleolus

      Senior Nerd

      In reply to jamie jardine

      Sure - I've worked in remote parts of Australia for a while and absolutely loved the night sky. However I don't think that human behaviour has necessarily changed that much in relation to the lunar cycle. If there was a genuine effect then we would have seen aberrant behaviour continue past the time when we had street lighting. I think there is also a difference between what you propose - that being light people might go out and do things more, which is a completely mundane and acceptable possibility, with the alternate view of some people that some mystical lunar influence changes human behaviour.

      Now you have me wondering about the light gathering capacity of equine eyes and how this differs between day and moonlight...

      report
    6. jamie jardine

      Acupuncturist

      In reply to Grendelus Malleolus

      Horses have wonderful night vision, even on a full moon in the thick of the forest I can't see my hand in front of my face, but my horse can see enough.

      Anyway, back to my original point, yes I agree that there are confounding factors in my theory, it's just that you'll find most myths contain a kernal of truth somewhere if you look deep enough.

      report
    7. Dennis Alexander

      logged in via LinkedIn

      In reply to Gary Campbell

      And, given the professionals using the term know about uncertainty and unpredictability, my guess is that the phrase gets used up to 2 weeks before and after the full moon. Indeed, I conjecture that a sociolinguistic analysis of the incidence of usage of the phrase "it must be the full moon" with actual occurrence of a full moon would not be statistically significantly greater than chance (about 1 in 28, I think;-)). A research opportunity for an honours thesis, perhaps.

      report
  2. Anna Alvsdotter

    logged in via Facebook

    Thank you, Clinical Senior male for clearing things up for us flimsy females who just don’t stop to think about Science and Statistics (or bother checking) in our rush to add more myths to folklore at social gatherings.

    report
    1. Michael Vagg

      Clinical Senior Lecturer at Deakin University School of Medicine & Pain Specialist at Barwon Health

      In reply to Anna Alvsdotter

      Anna

      Since more than half medical graduates have been women for the better part of a decade, most junior doctors are as well. Nursing has always been a profession where women have been in the majority. I chose to use a feminine pronoun in the introduction to the article because it is representative of both groups numerically. I don't think there is anything in the rest of the piece which argues that women are more superstitious or less scientific than men. No sexist overtone is intended, and neither did the (female) editor who checked the article before it was put up think there was one present. My apologies if this was how it appeared to you.

      report
    2. Anna Alvsdotter

      logged in via Facebook

      In reply to Michael Vagg

      Thank you Michael,
      I appreciate your sincere reply and certainly have no problem with the interesting facts presented in your piece. I believe sexist overtones are seldom intended, as they are culturally engrained in our mindset – often making us blind to them.
      In the public discourse we have to be vigilant against all kinds of stereotyping (gender, race, nationality, religion, age etc.) lest we cement unhelpful typical roles and traits, imagined or not. We also risk alienating a section of our audience, in this case women who are accustomed to but nevertheless tired of being stereotyped as creatures lacking in logic and critical thinking.
      I look forward to reading your next article. Kind regards

      report
    3. Clifford Chapman

      Retired English Teacher

      In reply to Anna Alvsdotter

      I do hope you don't mind me butting in, as it were, in your tete-a-tete, so to speak, woth Michael, but I find your comment: 'I believe sexist overtones are seldom intended, as they are culturally engrained in our mindset', most interesting and revealing, if the truth be told.

      Wouldn't that have to mean they were always intended and probably impossible not to occur, unless we really introduced ideological indoctrination into the socialisation process?

      It's not the freedom of thought that is the issue here but the force of nature, I'd probably settle for, when push comes to shove.

      Incidentally, at least Michael reads and responds to people's comments. I've raised a few points and asked point-blank one contributor to respond and his silence is deafening.

      report