Ever wonder if your Aunt’s story, about how “back in the day” when she was at college, all the girls in the dorm would get their periods on the Exact Same Day, was true?
The first reports of the apparent influence of social interactions on menstrual cycles was published over fifty years ago by Martha McClintock. The most common theories about how menstrual synchrony develops revolve around an idea of prolonged and frequent exposure to other females pheromones (i.e. chemical signals give off). Although, there are alternative ideas that menstrual synchronicity is some left over evolutionary advantage related to women archiving synchronized pregnancies and lactation windows -you know in case something happened to one of the mothers the other could “just take over.” 😳
More recent studies have shown that women living in pairs or triples do not actually synchronize their menstrual cycles. One such study showed that among nearly 100 women who lived together -and slept in the same room- for over five consecutive months! It has been suggested that the historical reports of menstrual synchronicity were the result of “methodological artifacts” resulting from study errors.
But in the spirit of never say never we aren’t saying that you haven’t felt the comradery you get from starting your period on the exact same day as your bestie. And undoubtedly, if it’s happened once you are probably more likely for it to happen again - especially if you’re both taking something like hormonal birth control that takes the guesswork out of when you’re next period will be. But, the population level phonomana of menstrual synchrony as a process that takes place over time to match up peoples cycles and that once established it persists —that idea has been largely debunked.
Science, Feminism, and Love
Ziomkiewicz A. (2006). Menstrual synchrony: Fact or artifact? Human nature (Hawthorne, N.Y.), 17(4), 419–432.
