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From The Economist - "Lunacy? People do not sleep easy on nights when there is a full Moon":

And the answer was “yes”, the phase of the Moon does affect human sleep patterns, even when the human involved cannot possibly see the Moon. Electroencephalography showed that the volunteers slept, on average, 20 minutes less around the time of the full Moon. It also took them five minutes longer to get to sleep, their delta activity (a measure of how deeply they were sleeping) was 30% lower than at other times, their level of melatonin, a sleep-related hormone, was reduced, and they reported, subjectively, that they had not slept as well as usual.

The referenced study doesn't meet my needs because I don't believe the data supports the conclusion attributed to it by the Economist.

Is it true that the phase of the Moon affects human sleep patterns?

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    Do you have any reason to doubt the study referenced (well, sort of) by The Economist? This is the link http://www.ncbi.nlm.nih.gov/pubmed/23891110 – nico Aug 18 '13 at 18:53
  • I doubt that the conclusion "the phase of the moon ***affects*** human sleep patterns" is supported by tr data in the study. –  Aug 18 '13 at 19:57
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    I didn't know we need to explain our reason for doubting a source. When was this requirement added? –  Aug 18 '13 at 19:58
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    It's not a requirement, it's just that, unless we understand your reason to doubt it, we don't understand what your standards of evidence are. You have the evidence in front of you: why don't you think the data in that study supports its conclusions? What would convince you? – Publius Aug 18 '13 at 20:03
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    This site isn't about convincing me. It's about examining the evidence behind scientific claims. I have *some* evidence in front of me. I don't presume to have all of it. If you believe the study supports the conclusion, say so in an answer. –  Aug 18 '13 at 20:17
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    I said so in a comment, as did nico – Publius Aug 19 '13 at 03:25
  • Also, what if the reason for my doubt is based on a strawman argument? Why would you present an answer that simply responds to *my* ignorant doubt? That's not very useful for other readers. –  Aug 19 '13 at 16:47
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    Your arguments are reasonable but http://skeptics.stackexchange.com/help/how-to-ask says, "`Tell us what you found and why it didn’t meet your needs`" -- so perhaps this (whether or when it's necessary to criticize your own sources in a question) should be a discussion topic for meta. – ChrisW Aug 19 '13 at 17:31
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    @Sancho: don't take it so personally. I just wanted to avoid writing an answer where I just quoted the study I linked above because I had the feeling that did not satisfy you and I wanted to hear why from you rather than trying to imagine it myself. – nico Aug 19 '13 at 17:48

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There are several very good reasons to doubt the results in the study you quoted.

First: It is a very small study. Only about 30 people took part, two nights per person. So the result was evaluated from only 64 datapoints. Even if the participants could not see the moon during the night, the author of the study himself says, he cannot be sure that they had not known about the fact, that the moon was full. Such knowledge can influence the result, when only one or two of the participants were expecting to sleep not very well, because they believe in these myths.

Second: There exist much larger studies in the same manner, that do not find any effects at all. As these studies are statistically much more significant, this is a very stron argument against the small study of Cajochen. There is for example the study of Klösch and Zeitlhofer evaluating more than 5000 nights (between 1997 and 2002) of about 400 participants. Not the least lunar effect was found in these data. It is highly unrealistic to assume, that the small study of Cajochen found an effect, that would not also have been significant in the larger study as larger studies have much better statistics than small ones.

Third: The result of the Cajochen study is by no means, what myths tell us about sleepless nights at full moon. Hey, the participants slept 5 minutes less. Who would even notice that in real life? Even if you believe the study has measured a real effect (what we can savely doubt, see above), your sleep quality is still much more depending on other effects. When you are troubled, this may keep you awake for much more than 5 minutes.

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Ute from Munich
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  • This seems like a good answer: but please give a more accurate/specific reference to the "study of Klösch and Zeitlhofer (between 1997 and 2002)" which you cited. For example is it `Zeitlhofer J, Kloesch G, Saletu B, Barbanoj MJ, Danker-Hopfe H, Kunz D, Himanen S-L, Kemp B, Penzel T, Roeschke J, Dorffner G. Is there a lunar effect on subjective and objective ratings of sleep quality? J Sleep Res 13, Suppl 1, 2004: 822`, or something else? And it would be even better to include a direct quote from the study, to support your statement that "Not the least lunar effect was found in these data". – ChrisW Aug 21 '13 at 10:30
  • Hi Chris, probably that's the right one; I have only a source in German - that's why I didn't cite it ib the first place. Zeitlhofer and Kloesch had a talk about the subject, which is cited here on page 10: http://www.schlafmedizin.at/newsletter/Newsletter01_2003.pdf They say: In keiner der zur Verfügung stehenden subjektiven Schlafbeurteilungen konnte ein signifikanter Unterschied zwischen den Vollmond- /Neumondnächten, den Nächten während des zunehmenden/abnehmenden Mondes und den als "neutral" eingestuften gefunden werden. - Means: No phase of the moon showed effects on the sleep quality. – Ute from Munich Aug 21 '13 at 14:47