In*Sync?
It’s the Grand National Debate Tournament in Washington, D.C. Exhausted from walking around in the humid D.C. heat, my roommates and I are sitting in our hotel room, ruminating over what to do. Someone mentions that our hotel has a pool.
“I can’t go swimming right now. I’m on my period,” I say, annoyed that I forgot to pack tampons.
With those words, I can tell I’ve struck a chord with my friends.
“Me too!” One of my teammates says, as she goes on to talk about her nasty cramps.
“That’s so weird, we’ve only been here for a day and already, our periods have synced!” Says my other roommate.
If you’ve ever menstruated, you can almost certainly recall a time when you and your friend, partner, or family member had your periods at the same time, and then, while feeling vindicated, you began to rattle off your extensive list of period complaints while your friend nodded their head in a knowing solidarity. We often see this menstrual overlap as a testament to how the strong bond of time has impacted our lives. We feel in awe with the biological wonder of our bodies and think that even though menses sucks, syncing up isn’t too bad. But do menstruators actually sync up? Unfortunately, the answer is no.
The old wives’ tale of menstrual synchrony, the psychological theory that the menstrual cycles of people in close proximity to each other will have similar timings, find its scientific origins from the University of Chicago psychologist Martha McClintock’s seminal research “Menstrual Synchrony and Suppression” in the scientific journal Nature in 1971. During her undergraduate years at Wellesley College, she questioned 135 undergraduate menstruators between the ages of 17 to 22 who lived in dormitories about the start dates of their periods. From her observations, she deduced that menstruators who were in close friend groups or roommates had intersecting period cycles. The results of the study seemed to suggest that the “significant factor in synchrony is … that the individuals of the group spend some time together.” Her study was one of the first to propose the effects of pheromones, chemicals released by animals that influence the behavior of others of the same species, on menstrual synchrony. Soon, menstrual synchrony was nicknamed “the McClintock effect,” paying homage to the pioneering female scientist who investigated the phenomenon.
Before the scientific inquiry into menstrual synchrony, it was believed that menstruators’ cycles were affected by the lunar phases. Along with this archaic supposition, the McClintock effect has not withstood the test of time. McClintock’s work has been criticized by H. Clyde Wilson, a professor of anthropology at the University of Missouri-Columbia in 1992, as having methodological and statistical errors, like not following the menstruators for a lengthy amount of time and problems with the sample size. A plethora of researchers, from Leonard and Aron Weller of Bar-Ilan University in Israel to Jeffrey Schank at the University of California, Davis, to Marija Vlajic, a data scientist who worked with the fertility app Clue and Oxford University, have quashed the McClintock effect. The true wonder of menstrual synchrony is mathematical chance. Some menstruators have differing lengths of cycles, and a menstruator with a four-week cycle and a menstruator with a six-week cycle will coincide eventually. Menstrual synchronization seems significant when it is viewed in a shorter time frame. As for the pheromonal explanation, humans lack vomeronasal organs (VNO), a major organ in the primate pheromonal communication highway, and there is currently no research that can conclude that pheromones cause menstrual synchrony.
So even though this myth has been debunked, why does it still persist? Our shared bleeding, bloating, cramps, hunger cravings, and period stigma bind and liberate menstruators. Our periods fortify our sisterhood and unity. While our menstrual cycles cross because of mathematical chance, there is nothing serendipitous or shameful about being a bleeding, powerful menstruator.
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Relevant References and Footnotes
https://www.scientificamerican.com/article/do-women-who-live-together-menstruate-together/
https://health.clevelandclinic.org/myth-truth-period-really-sync-close-friends/
https://www.cbc.ca/life/wellness/blood-sisters-do-women-s-menstrual-cycles-really-sync-up-1.4086564
