"Period-syncing" is a myth
No matter how inaccurate the myth of period syncing may be, the idea
that women’s bodies can fall into collective rhythms carries a certain
mysterious, otherworldly appeal and, lending the myth more inertia,
gives women a way to feel connection, empathy, and collective
empowerment with other women.
Period syncing—or, more formally, “menstrual synchrony”—was introduced
into the popular consciousness in 1971 by a researcher named Martha
McClintock. Her study on the menstruation patterns of students at a
women’s college, published in the journal Nature,
tracked the period start dates of 135 women who lived together in a
dormitory over a time frame of about six months. It claimed to find “a
significant increase in synchronization (that is, a decrease in the
difference between onset dates)” among roommates and among groups of
women who independently identified one another as a “close friend.” At
the beginning of the study, these friends averaged about six and a half
days’ difference between period start dates. By the end, they averaged a
little less than five. (McClintock conducted this research while she
was still an undergraduate at Wellesley College.)..
In a 1999 paper in the journal Human Reproduction, Strassmann pointed out a fundamental flaw in the period-syncing logic:
Given a cycle length of 28 days (not the rule—but an example), the
maximum that two women can be out of phase is 14 days. On average, the
onsets will be 7 days apart. Fully half the time they should be even
closer. Given that menstruation often lasts 5 days, it is not surprising
that friends commonly experience overlapping menses, which is taken as
personal confirmation of menstrual synchrony.
Strassmann considers the idea of period syncing to have been “debunked,”
but of course much of the general population remains convinced that
it’s a real thing, thanks to what she calls “an appealing narrative that
overrides the science.”
Discussed at length in
The Atlantic.
I could never figure out why I should care about it.
ReplyDeleteThe myth of the 28day cycle needs to die, particularly as the basis for any sort of study. Only 10-15% of women have a natural 28 day cycle. Using that number and the 14 day "halves" of the cycle as if they are common or average is complete misunderstanding of women's cycles at the very start of the work. It's the basis of the due date calculator wheel that is used to forecast pregnancy due dates as well, which is insanity, when it will only be anything like accurate for a small minority of women.
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