A few days ago we had a full moon. A lengthy discussion about the effect of a full moon on hospital admissions took place on Twitter.
Many papers say admissions increase and odd things happen, and many others have found there is no relationship between the phases of the moon and anything that goes on in hospitals.
Someone sent me a link to a paper that a lot of devotees of astrology like to quote. It's called "The influence of the full moon on the number of admissions related to gastrointestinal bleeding," and it appeared in the International Journal of Nursing Practice in 2004.
The authors looked at the records of 447 consecutive patients admitted with G.I. bleeding to a hospital in Barcelona over two years. There were 26 (an average of 1.04 ± 0.93) admissions during 25 days of the full moon and 421 (0.59 ± 0.78) admissions on the other 713 days where the moon was not full, P = 0.007.
The authors concluded "the number of admissions related to gastrointestinal hemorrhage in our bleeding unit increases during [a] full moon. However, the wide variation in the number of admissions throughout the lunar cycle, as well as the possible influence of other external factors such as atmospheric phenomena, and concomitant with the lunar cycle, could limit analysis and interpretation of the results."
Jean-Luc Margot, a UCLA professor of physics and astronomy, published a detailed critique of the of the above paper in the journal Nursing Research. He pointed out a number of problems. I will share a simple one.
This figure represents the number of admissions for G.I. bleeding plotted against the days of the lunar cycle.
Here is the figure again with some of the other days highlighted.
Of course another major problem is even if there were significantly more admissions on the day of the full moon, the paper does not prove that the moon was the cause.
Maybe the full moon does affect hospital admissions, but the astrologers won't convince me without a lot better study than the one from Spain.