Some researchers have hypothesized that, historically, women tended to menstruate whenever there was a new moon – and that it’s only our modern way of living (in houses with artificial light) that stopped our periods synchronizing with the full moon. Of course, in the world as we know it today a woman’s menstrual cycle does not synchronize with the lunar cycle (or even with other women’s cycles when they live in close proximity). However the lack of a menstrual-lunar cycle correlation could be simply due to our modern lifestyles (e.g. living in walled houses with roofs over our head and using artificial lighting). Is there any truth to the idea that historically women’s menstrual cycles tended to synchronize with certain phases of the moon?
Cultural connections between menstruation and the moon:
The moon was regarded as a powerful force by many cultures and religions historically (some even identified it as a god). Today science has proven that the moon has a strong influence over aspects of our world – we now know that the moon is a powerful magnetic force that controls our coastal tides (tides are highest at new moon or full moon).
Menstrual cycles and the lunar cycle are similar in length, therefore menstruation and fertility have long been associated with the moon. Many women today refer to their period as their “moon time”, or to their menstrual cup as their “moon cup”. The new moon is called “the day of the blood” by the Ashanti people, and the Yoruba believe that if they were to work in the fields that day the corn and rice would turn blood red.
How would society be different if menstrual cycles correlated with the lunar cycle?
If women could menstruate together at each new moon we would have solidarity in our experiences and we wouldn’t feel so secretive about menstruation and isolated in our own individual experiences. Menstruation would become something women talked about more because we would all be experiencing it together. And wouldn’t it be great if women could predict their own menstrual cycles? I would love to be able to predict my menstrual cycle. If women menstruated, as a group, with the new moon we would probably feel like we had a greater connection with nature. It would also make me feel a little bit like a werewolf if I was able to synchronize my cycle with the moon!
If there is a natural connection between women’s menstrual cycles and the moon, we could figure out what was obstructing this connection (e.g. using artifical lighting after the sun sets), and what could be done to reduce the impact of these obstructions and ‘re-synch’ our cycles with the moon (e.g. stare at the moon for a few minutes before going to bed…?)
What the research has found:
I like the idea that women with no access to artificial lighting, who slept under the stars every night (or in tents outside), had menstrual cycles that tended to synchronize with certain phases of the moon. However no evidence has been found that menstrual cycles can synchronize with the lunar cycle. A meta-analysis of studies from 1996 showed no correlation between the human menstrual cycle and the lunar cycle. For example, no correlation was found between the menstrual and lunar cycles for Dogon villagers even though they had no electric lighting and spent most nights outdoors.
So women don’t have a special connection to nature after all! We just menstruate whenever our bodies decide to, and our bodies don’t pay any special attention to the moon. I suppose that is clever of our bodies – we’d probably end up with messed up menstrual cycles & a whole host of fertility issues if women’s menstrual cycles had to correlate with the moon no matter what. I mean, really, what does the moon have to do with women’s menstrual cycles? Pretty much absolutely nothing. A lot of the time the only visible sign of a women’s menstrual cycle is her period – however the 28-odd day menstrual cycle is a complex process with lots of little changes along the way that are necessary for a woman to achieve a healthy and fertile menstrual cycle. As long as all the little stages/processes within the menstrual cycle happen within the right time frame for our individual cycles (e.g. our period starts 11-15ish days after we ovulate, and no fewer than 9 days after ovulation) then that’s all that matters.
Is there any correlation between the lunar cycle and human or animal behaviour?
There have been many studies examining whether there is any connection between the lunar cycle and human or animal behaviour (not just menstruation) and no connection has been found. According to Wikipedia: “The term lunar effect refers to the belief that there is correlation between specific stages of the Earth’s lunar cycle and behavior in animals, including humans, that cannot simply be explained by variation in light levels. A considerable number of studies have examined the belief: by the late 1980s, there were at least 40 published studies on the purported lunar-lunacy connection, and at least 20 published studies on the purported lunar-birthrate connection. Several extensive literature reviews and meta-analyses have found no correlation between the lunar cycle and human biology or behavior.”
- “ovulation tends to occur at the full moon; and menstruation at the new moon” – no evidence for this has been found.
- “The birth rate increases at a full moon” – no evidence for this has been found.
- “surgeons shouldn’t operate on the full moon because of the increased risk of death of the patient through blood loss:
- “People with mental disorders generally exhibit increased violent or aggressive behaviour during the full moon”
- “There are more incidents of crime and aggressive/disorderly behaviour during a full moon”
- “The lunar cycle is correlated with sleep quality” – there is some evidence that this might be true (even if a person cannot see the moon and doesn’t know what phase the moon is in). A 2013 study by University of Basel in Switzerland found that participants took 5 minutes longer to get to sleep during a full moon, had about 20 minutes less sleep during the night, and had less deep sleep. The participants were in stringently controlled conditions. Stringently controlled laboratory conditions, in a cross-sectional setting, were employed to exclude confounding effects such as increased light at night or the potential bias in perception.