Skeptics Stack Exchange is a question and answer site for scientific skepticism. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I recall reading an article, many years ago, in the New Scientist concerning a study into the effect of the lunar cycle on men. It was suggested that some men showed a physical response, such as a change in the rate of beard growth.

I don't know if it was part of the NS article, but this has obvious links with werewolf stories.

I have a kind of wish for this to be true. It seems feasible that some response to the moon should exist in men as well as women, given our evolution in the presence of that near neighbour.

Edit, further information:

While the orbital period of the Moon is 27.322 days, Wolfram Research state that the mean time for one lunar phase cycle (i.e., the synodic period of the Moon) is 29.530589 days.

An article on the Biology Online website cites research into lunar influence on animals and plants. This does not specifically mention the influence on men but, more generally, animals.

share|improve this question
Please improve this question by adding references. – Sklivvz Mar 12 '11 at 12:19
I think it confuses the question to bring up the moon. It's still valid to ask if men, like women, have biological cycles of about that length. It's certainly possible. I'd be interested to know. – Mike Dunlavey Mar 12 '11 at 18:06
@Mike. Good point. Perhaps I should have left the question more open-ended, but my own (unscientific) view is that it is likely the Moon affects Life on Earth beyond the sea tides. With this in mind, and in response to other answers here, I've added references to Moon period data and research into effects on animals. If this confuses things further, I guess the question may be closed :( – Zzzzzzz123 Mar 13 '11 at 10:59
"Men’s testosterone appears to cycle throughout the day, month, and possibly even the seasons, affecting their moods and sexual desire. ... But what about men? Do they have hormonal cycles too? Some hormones researchers say no; men don’t cycle. Others say yes, but their cycles are less studied and less dramatic than women’s. Men’s testosterone cycles fluctuate from higher in the morning to lower each evening, and, according to some ... studies, the hormone level fluctuates seasonally as well, peaking in October and ebbing in April" – A E Mar 2 '15 at 23:34

The lunar cycle has no effect on human behavior in any way. No scientific study ever conducted has shown any correlation between the moon cycles and any human activity.

See Wikipedia's article on the Lunar Effect for a good summary of studies conducted:

Psychologist Ivan Kelly of the University of Saskatchewan (with James Rotton and Roger Culver) did a meta-analysis of thirty-seven studies that examined relationships between the moon's four phases and human behavior in 1996. The meta-analysis revealed no significant correlation. They also checked twenty-three studies that had claimed to show correlation, and nearly half of these contained at least one statistical error. 1

1: Kelly, Ivan; Rotton, James; Culver, Roger (1986), "The Moon Was Full and Nothing Happened: A Review of Studies on the Moon and Human Behavior", Skeptical Inquirer 10 (2): 129–43. Reprinted in The Hundredth Monkey - and other paradigms of the paranormal, edited by Kendrick Frazier, Prometheus Books. Revised and updated in The Outer Edge: Classic Investigations of the Paranormal, edited by Joe Nickell, Barry Karr, and Tom Genoni, 1996, CSICOP.

share|improve this answer
How is this relevant? He is talking about beard growth and you're talking about human behavior. – Borror0 Mar 12 '11 at 4:01
@Borror0 He asked about physical response. Beard growth was just one example. And even with beard growth, the force of gravity exerted by your bed pillow is stronger than the moon's gravity, so the one possible influence the moon could have is pretty irrelevant. – Dan Herbert Mar 12 '11 at 5:09
Please improve this answer by using better citations than wikipedia – Sklivvz Mar 12 '11 at 12:20
See… : "[sites like wikipedia] are not deemed reliable enough to justify a statement". – Sklivvz Mar 12 '11 at 14:36
@SKlivvz: Double standards? Here is a posting with 3 citations of wikipedia:… plus Photoshop Disasters. Other sources may as well be unavailable in the future - wikipedia is at least easily available now. – user unknown Mar 13 '11 at 2:59

While women do have something like a monthly cycle it's not linked to the moon. The mean cycle length is 29.1 days while the moon cycle is 27.3 days.

Even if there would be a monthly cycle among men it's therefore unlikely that it would sync with the moon. It would make much more sense if a possible monthly cycle would sync with the cycle of a nearby female.

share|improve this answer
I've added some reference links to my original question, including one to a source stating that the average period of the moon is 29.5 days. There's also an article on the moon's effects on animal and plant life. – Zzzzzzz123 Mar 13 '11 at 10:26
@Zzzzzzz123: The moon cirles around the earth, and together with the earth around the sun. So while the orbit is 27.3 days, the angle towards the sun is about 360°/12 off after one month which explains while a mooncyle is about 2 days longer. See the picture below. – user unknown Jun 16 '15 at 1:08

How should that work? Should the moon pull on the beard? Well - there is a gravitation effect from the moon, but it's way too weak to do anything with your beard, and it's in effect whether we face the illuminated side of the moon as the not illuminated side of the moon - it's the same distance and the same moon. The only difference is the amount of light which is reflected to the earth. The gravitational force of the earth itself is x-times stronger, as you can see if you try to leave the earth vertically.

Well, and we have much more artificial light than moonlight. Sometimes we don't have moon light on full moon because of clouds, or we don't leave our house.

Should there be a darwinistic advantage of beard growth in full moon phases? Which should that been? To spend more shadow?

To refresh your idea about the mooncycle, I made this schematic drawing schematic drawing .

The lower repetition shall show, that the moon, most often isn't in the earth shadow when behind the earth, viewed from the sun, but shifted up or down.

share|improve this answer
The OP does not need to necessarily have a theory, as we argued before... – Sklivvz Mar 12 '11 at 12:20
Who is 'we'? You and ...? – user unknown Mar 12 '11 at 15:45
@user: correlation and causation are different things. Asking if there is a correlation is a skeptical question and does not require a theory. Think about it: before you can think of a theory you should always verify that there is something to explain at all! Only after you have proof of an effect you should start thinking about a cause. – Sklivvz Mar 12 '11 at 19:29
If you think the question is bad, you have to flag the question, because it didn't talk about correlation, but causuation. Refering me to a discussion you escaped, while inviting me to the chat, where you didn't show up - what's the idea behind that? – user unknown Mar 12 '11 at 20:09
This doesn't address the question, as you seem to be confusing an example with the actual question (the phrase "such as" means that beard growth is just one possible outcome). You provide no references, and the picture has no relevance to the actual question. – Beofett Aug 9 '11 at 16:09

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.