Moons + Periods: Are they related?

Throughout the ages, the moon has been thought to be linked to menstrual cycles. In fact, there are even nicknames for periods such as 'moon cycle' or 'moon time' that resulted from this belief. They were thought to be related because of the similarity in lengths of cycles. 

The length of a revolution of the moon (time it takes to go all the way around the earth) is a little over 27 days. A moon phase cycle, which are the phases of the moon that we see, lasts 29.5 days. Menstrual cycles typically last between 25-30 days so the lengths of time are very similar for moon cycles and menstrual cycles.

Aristotle even said, ““[T]he menses tend to occur naturally during the waning moon […]. For this time of the month is colder and more humid because of the wasting and disappearance of the Moon.”


But is there a link? Or is it just an ancient myth?


In 1986 a study was conducted by the Canton Traditional Chinese Medical College in Guangzhou, China. The study “was based on the concept of traditional Chinese medicine that human physiological rhythms display synergism with other natural rhythms.” The study included 826 female participants ages 16-25 and studied their cycles over 4 months in different seasons. The results from the study showed that a large portion of menstruations occurred around a new moon. 


However, more recent studies have contradicted the findings of the 1986 study. In 2013 a study was published that monitored 980 menstrual cycles in 74 women over the course of a year and found no synchronicity between the menstrual cycles and lunar cycles.


A study conducted by the Clue app in 2016 used data from 1.5 million Clue users. The researchers found that periods fell randomly throughout the month and there was no relation to the lunar cycle.


A new study is looking at a small group of 22 participants who kept track of their menstrual cycles for up to 32 years. The study found that cycles intermittently synced with the cycles of the moon. Researchers found that this synchronicity only lasted for a short period of the participants' lives and became less likely to happen as they got older.

Researchers from this study hypothesize that in ancient times menstrual cycles were more synced with the moon but modern exposure to artificial light among other things has changed this. They do not yet have proof for this theory.

Charlotte Helfrich-Forster, a professor working on the study, suggests that while we don't yet know what this study means as far as the impact on our lives, the worse case scenario would suggest that the modern lack of synchronicity with the moon could result in less fertility.


While most of the evidence seems to suggest that there is not a correlation between moon cycles and periods, we still aren't 100% sure that there is no correlation. What do you think? Would our periods be synched with the cycle of the moon if it weren't for modern technology?

Source: Medical News Today

Photo by Sanni Sahil on Unsplash

Leave a comment

All comments are moderated before being published