If you’re a woman, you’ve likely heard about the phenomenon of periods “syncing up” between friends or roommates. Maybe you and your sister somehow ended up with the same cycle timing, or perhaps your cycle was late one month, so your period ended up falling during your roommate’s period.
These coincidences might have convinced you that your cycle was actually “syncing up” with other women in your life’s cycles. But is that actually possible?
I spoke with women’s health experts on this common assumption to better understand the concept and its validity. Let’s dive in.
Can Women’s periods Actually Sync Up?
Contrary to popular belief, women’s cycles don’t actually sync up—at least, not according to science.
“The concept comes from a small study in the ‘70s, but researchers after this couldn’t really replicate the results,” says Dr Jody-Ann McLean (MBBCh, BSc), medical doctor and medical writer with expertise in women’s hormonal and metabolic health. “There’s a more recent analysis from 2017 where researchers from the University of Oxford and the period-tracking app Clue found that women’s cycles actually drifted further apart over time instead of syncing.”
“Although it is common for friends, roommates, or family members to recognize when their cycle timing occurs at approximately the same time, this has been found by researchers to occur mostly by coincidence rather than through some biological process that causes synchronized timing,” adds Kat Grassetti, LCSW, Women’s Health Specialist and Clinical Director at Monima Wellness Center.
Not only is there no evidence, but there’s also no proven mechanism that would cause menstrual cycles to sync up, Grassetti adds.
“Formerly, researchers theorized that some sort of pheromone could possibly affect when each woman would have her next menstruation; however, after much additional study, the majority of the scientific community cannot find evidence to support this theory,” she says. “As such, most researchers today see menstrual synchrony (if it exists) as simply an interesting observation in which there is still no clear proof of its occurrence.”
What Prompted The Misconception About Women’s Cycles?
For decades, many people have believed this idea to be true. I’ve even noticed myself “syncing up” with some of my friends’ cycles when vacationing together or living in close quarters. But really, this was mere coincidence.
“There are many variations to each woman’s monthly menstrual cycle; as such, the coincidence of aligned or near-aligned periods is likely to occur occasionally,” says Grassetti. “Conversely, the number of times that the couple’s cycles don’t appear to match at all would likely far exceed the number of times when they do match.”
McLean labels the experiences as more of a “confirmation bias,” often a way of seeking community and support.
“If you think about the statistical side of this, cycles vary quite a lot in length and periods last a few days to a week, so two women who spend a lot of time with each other have a decent chance of overlapping periods at some point, just from pure coincidence,” she explains. “You’re probably also going to remember the months that your periods do align, and maybe forget the ones where you don’t.”
The post Your Friends Swear Their Periods Sync Up. I Asked Experts for the Truth. appeared first on VICE.
