Alvergne has tried to review the evidence for this phenomenon. She says the idea started with research findings published in Nature , a scientific journal, in A researcher called Martha McClintock studied the menstrual cycles of women in an American college. Dr McClintock hypothesised that this was because the women who were spending time together had the chance for their pheromones to affect each other.
And why would this happen? The most prevalent theory was that it was an evolved strategy among females to co-operate with each other - to stop becoming a kind of harem for a single dominant man.
The idea is that if women had synchronised cycles, they would all be fertile at the same time - so one man would not be able to reproduce with them all. In the s when this paper came out, feminism was emerging as an important movement.
Alvergne thinks this may be one of the reasons the idea became so popular. And from a feminist point of view, the idea that females would co-operate in the face of male domination is attractive.
Other studies, some in humans and some in other primates, seemed to show similar results. But, there were also studies that didn't find evidence of periods syncing. And people started to pick holes in the earlier research - critics identified problems in the people chosen for the study.
The definition of when they were syncing was quite loose. Perhaps most importantly, critics pointed to the fact that in McClintock's findings she didn't account for chance to explain why women's cycles were in sync. This seems to go against what many women feel they experience. It just wants to be one of the girls. Not only that but Inez thinks some women have wombs that prefer to play a leadership role.
That women synchronize to each other, however, is a myth. Subsequent studies from the last couple of decades continue to suggest that menstrual syncing with people around you is not a likely occurrence. First, the study of college students we mentioned earlier demonstrated that:. Then, 11 years later, researchers from a period-tracking app alongside Oxford University collected digital data from app users in a pilot study to observe changes in cycle length and occurrences of period syncing versus diverging.
FYI, this pilot study hasn't been published anywhere but the app's blog so far. After receiving over 1, responses and narrowing it down to pairs of users whose cycles occurred at similar times, they tracked three consecutive cycles for each pair. Here are their most significant findings:. Side note: We're thrilled to catch a glimpse of all the possibilities that can come from opting into research with a period-tracking app.
As the Cleveland Clinic tells us, period syncing often comes down to a simple matter of time, rather than any kind of biological phenomenon. Hormonal birth control , stress , medications, health conditions, and disordered eating can all interrupt your usual cycle.
While the study from the app team and Oxford doctor never moved past the "pilot" phase and into a peer-reviewed journal, the sample size was the largest compared to past studies. If you're interested in moving fertility and reproductive health research forward, check out what we're working on at Modern Fertility and get in on the action.
So, feel free to keep on knowingly nodding when friends or family members ask to borrow a tampon. English Taylor is a San Francisco-based writer and birth doula. Advertising Policy. You have successfully subscribed to our newsletter. Related Articles. Why Is My Period Late? Tired of Tampons? Trending Topics. What Parents Need to Know.
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