After seeing my GP about a wart on my knee she suggested that any removal should be done while the moon is waning in order to improve recovery. This sounded, to put it mildly, odd to me. Have there been any studies that provide evidence for a relationship between the moon cycle and recovery from surgery? If the answer is yes, is it due to another manifestation of the placebo effect?


1 Answer 1


The idea that the lunar cycle has a direct effect on human physiology (apart from having slightly more light to see by, or planning fishing trips based on the tides) has had a long history. The concept is known as the Lunar Effect, and is maintained by confirmation bias and under-sampled studies testing against every conceivable effect that turn out to be unreproduceable.

Your GP seems to be referring to this study, which did come to the conclusion that the waning moon seems to have an effect on the recovery of patients, but only for the recovery of Aortic dissection repair.

The full-moon cycle appeared to reduce the odds of death, and the full-moon cycle, along with being male and requiring a concomitant cardiac procedure, was associated with shorter LOS (length of stay).

A slightly older study, with much large sample size (over 18,500 patients rather than 210), did not find a similar effect:

The number of cases each weekday, each month of the year, and during each phase of the moon were consistent. None of the time factors significantly affected the composite morbidity outcome.

My suspicion would be sampling bias, especially with the small positive results.

  • The placebo or nocebo effect could also have an impact and is very difficult to control for.
    – rjzii
    Commented Oct 23, 2013 at 11:47
  • @Rob the big study suggests any placebo effect is too minor to be significant.
    – Oddthinking
    Commented Oct 23, 2013 at 14:49
  • @Oddthinking Which would imply that the larger study was able to control for it where as the smaller one didn't, ;)
    – rjzii
    Commented Oct 23, 2013 at 16:35

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