Does your Period Sync With Your Roommate?

If films and TV shows are to be believed the ultimate sign of female friendship or camaraderie is the converted ‘cycle sync’. It is estimated that almost 80% of women believe in this effect.

While living or working with someone who rushes to the bathroom as the same time as you and is doubled over with painful cramps at the same time as you can be weirdly comforting, period syncing, unfortunately, is a huge myth. 

The Origins: 

The perception that your menstrual cycle can sync up with people around you has been an old wives’ tale, especially in the West, passed down from mother to daughter (funnily enough, did none of the pairs notice THEIR period wasn’t syncing up?). The first “academic” mention of the phenomena appears in a paper in 1971 when a researcher called Martha McClintock spoke to over a hundred college age girls residing in the same dormitory at Wellesley College, seeking to establish that their menstrual cycles would sync up. She asked them to track their monthly cycles and from the data presented to her concluded the existence of menstrual synchrony. Looking into the research, you’ll find that she defined ‘Menstrual synchrony’ as ‘when the menstrual cycle onsets of two or more women become closer together in time than they were several months earlier’. 

Her reasoning for the supposed synchrony was pheromones or even the lunar cycle!

As a result of her research, the effect is also called “the McClintock effect.”

Research into menstruation, though severely lacking, has often tried to establish a cause and effect relationship. In an old study from 1986, with 862 people, over 28% of participants experienced period bleeding during the new moon. This led to the conclusion that there exists some form of a relationship between the moon and women’s period cycles, because of course, we’re all just secretly werewolves in disguise. 

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The Truth:

It goes without saying that subsequent research failed to replicate McClintock’s findings. A new study in 2006 found that women do not sync their menstrual cycles. This study involved collecting data from 186 women living in groups in a dormitory in China.

The advent of period tracking apps has also made it clear. Infact, one of the largest research on the topic was done by Oxford University in conjunction with Clue collected data from over 1,500 people to demonstrate that close proximity does not sync up women’s period cycles. Researchers first asked app users if they thought their menstrual cycle synced with another user’s cycle, as well as their relationship with this other person (i.e. friends, siblings, partners, roommates, coworkers, etc.), if they lived together, and if they were on hormonal birth control. After receiving over 1,500 responses and narrowing it down to 360 pairs of users whose cycles occurred at similar times, they tracked three consecutive cycles for each pair.

Latest Studies that State the opposite? 

Some latest studies have actually come to the conclusion that far from syncing,  menstrual diverging might be an actual phenomenon. The Clue and Oxford University study mentioned above actually discovered that about 273 pairs of people, which comprised about 78% of the people actually had a bigger difference in their cycle start dates by the end of the study period. 

The research is, however, not published as of now and only a pilot study available on the Clue App. 

The fact of the matter is, as Cleveland Clinic put it, period syncing comes down to a simple matter of time rather than the pheromones of other women around you. For instance, if you live with another menstruator for at least a year, the 4 - 5 weeks average cycle would eventually coincide at some point and diverge at others. Menstrual synchrony might often appear due to the laws of probability more than anything else.This probability also complicates research into period syncing.

That doesn’t mean you can’t still cozy up with your roommate and share those chocolate snacks and complain about cramps together!