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Do women’s periods really sync when they live together? Here’s the truth

Published on:22 January 2021, 17:36pm IST
We often hear that periods coincide in women who live with each other. But is this just another theory or is it true? Let’s find out now.
Geetika Sachdev
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Period syncing: does it really happen? Image courtesy: Shutterstock
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Haven’t we all come across stories where women get periods at the same time? This happens, especially when they live together. But is it just a mere coincidence or is there any truth to it? Several theories suggest that this syncing of menstrual cycles is because women’s pheromones interact with each other, causing their periods to happen at the same time. 

This phenomenon is also called ‘menstrual synchrony’ or the ‘McClintock effect’, and there are so many women in the world who believe this is really a thing! But there’s hardly any medical literature to prove it. Others say there’s an alpha female who influences the entire group. 

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In this article, we will try to understand what period syncing is all about, and is it real or just another myth?

The period syncing effect

It is said that period syncing is passed down from mothers to their daughters, but this phenomenon got some attention when a researcher named Martha McClintock conducted a study of 135 college women living in a hostel together to see if their menstrual cycles matched. No other factor was taken into consideration, apart from when the women started to bleed. The study concluded that women’s periods do sync up. 

But does it have any relevance today? Well, there are several period tracking apps and some other literature that shows that period syncing is probably a coincidence. A study conducted in 2006 asserted that ‘women do not sync their menstrual cycle’. The study had collected information from 186 women who were living in a hostel in China. It was then concluded that any sort of period syncing that happened was just a case of mathematical coincidence. 

period syncing
Women’s period really sync! Image Courtesy: Shutterstock

Another study conducted by Oxford University in collaboration with the period tracking app company Clue showed that it is highly impossible that women affect each other’s menstrual cycles by being in close contact to one another. 

Do our cycles sync with the moon?

If we look at the concept of menstruation, it is often believed that women’s cycles are closely linked with the lunar cycle. There’s also some research to show that your period is affected by the moon’s several phases.

A study conducted in 1986 revealed that over 28% of participants had their menstrual cycles during the new moon phase. It also concluded that 1 in 4 women have their period during the new moon. 

Period syncing
Does period sync with the moon? Image courtesy: Shutterstock
Period syncing is hard to prove

Well, let’s break it to you: period syncing is pretty hard to prove. The thing is we might never be able to conclusively prove that this phenomenon really exists. As mentioned above, it relies on the fact that women’s pheromones interact with each other, and thus syncing happens. For the uninitiated, pheromones are chemical signals that we pass on to other humans around us. They are often attached to feelings like attraction and sexual arousal, among other things. But does this really happen in case of women and their menstrual cycles?

Also, every woman’s menstrual cycle is different. On average, it happens for five to seven days, but there are many women who do not bleed all these days. Some have shorter periods, others don’t even have them. That’s what makes period syncing such a subjective subject. 

All in all, period syncing is more about the laws of probability than anything else. As humans, we tend to find different ways to connect more emotionally with those who are close to us. However, it is important to note that not having your period in sync with your roommate doesn’t mean you are not close!

Geetika Sachdev Geetika Sachdev

An independent writer and journalist, Geetika loves sharp and fresh humour, just like her coffee! If not writing, you'll find her cafe-hopping and raiding the best book stores in town.