Ever notice that you seem to share “that time of the month” with your closest friends and coworkers? It's not a total concidence.
“Menstrual synchrony”—the idea that women who live together (or near one another) get their periods around the same time—dates back to the 1970s and has been discussed in dorm rooms ever since. But is there any truth to the rumors?
Some research says yes—namely a 1971 study published in the journal Nature by psychologist Martha McClintock. Her research was the first to demonstrate just what we all believed in college: Ladies who live in close proximity do indeed see their flows sync up—in part thanks to odorless chemicals we give off called pheromones, which could impact behavior and physiology.
But McClintock’s original research wasn’t perfect. Some later studies were able to replicate her findings (and show that ladies who lived together bled together), but others were not.
So what’s the verdict? To date, researchers aren’t quite sure. While the clinical data pointing to an affirmative, clear-cut, research-backed sync-up between friends is certainly lacking, anecdotal and empirical evidence still points to the possibility.
Alyssa Dweck, M.D., an ob-gyn at the Mount Kisco Medical Group and author of V Is for Vagina, says it’s not uncommon to see mothers and daughters or roommates menstruating together.
But Dweck notes that there are other explanations beyond a few shared pheromones. For example, people in close proximity to each other may have similar diets, exercise routines, sleep/wake cycles, and shared stressors—all of which can influence menstrual habits, she says.
Another point worth noting: While Dweck says she’s seen women on the Pill sync up (even though their cycles are controlled chemically), ladies also tend to start birth control on the same day: Sunday. So, sure, living together may play a role in cramping together, but so could the fact that your roomie started her pack on the same Sunday, too.
The bottom line: Misery loves company, and while researchers sort out the science, we’ll gladly take a few friends to share the pains of PMS (and joys of ice cream) with.