A menstruating woman is like a boiling pot ready to explode with emotions. It is not the woman but her hormones that are to be blamed for this! How about coming across a group of women who menstruate at the same time? It might seem highly unlikely but it does indeed happen in every part of the world unofficially termed as ‘period syncing.’ Quite new to many, this term has been highlighted in many of our web series enlightening people’s knowledge about synced menstruations. For those unaware, period syncing is a term to define women who spend more and more time together that they start menstruating on the same date every month.
The McClintock Effect
Though the idea of period syncing was passed on from one generation to the other (great grandma to grandma, grandma to mom, mom to child and so on) the theory was conceptualized way back in 1971 by a researcher named Martha McClintock. The study conducted on 135 women who lived in a dormitory for a period of over 6 months was published in the reputed journal ‘Nature.’ The study found a definite synchronization among roommates and groups of women who identified each other as their closest friend than among random pairing of women-while the difference in period start day was almost 6.5 days apart in these besties and it was reduced to less than 5 days at the end. Though the researcher did not give scientific explanations backing the theory, the most prevalent theory was that it was an evolved strategy for preventing women from becoming a harem for a man (https://www.bbc.com/news/magazine-37256161).
Period syncing was also called as the ‘McClintock Effect’ named after the researcher and this study was quoted often until 1978 but a researcher in 1992 pointed out serious mistakes in the study. Replication of the study often did not bring out the same desirable effect but it was not until 1999 that a researcher called Strassmann brought into limelight a fundamental flaw in the period-syncing logic. According to him, women commonly have a 28-day cycle and the maximum that two women can be out of phase is for 14 days. Onset would be 7 days apart and more than 50% times they should be even closer. Menstrual cycles last from 5-8 days and hence, it is not uncommon to see friends/family experience overlapping period cycles. According to his theory, most women have their periods at the same time as other women but we simply don’t know because women don’t keep going around publicizing their period cycles. Yet another study in 2006 on a group of 186 women living in a dorm in China showed that women don’t sync up their periods. But another study in 2017 found that 44% participants involved in the study experienced period syncing.
The word ‘menstruation’ is derived from a combination of Latin and Greek words meaning ‘moon’ and ‘month’. According to a 1986 study, 1 in every 4 women have periods during the new moon phase and it is hence, not highly surprising that a group of women staying together might experience similar period cycles.
There are also beliefs among women that when women spend a significant amount of time together their periods are synced to one of the women’s cycle and it is usually in line with the dominant woman. Though there is no theory behind the idea we have always as a society believed in dominance and hierarchy and it is no surprise that it is the dominant woman’s cycle that’s become the norm for other people in the group.
Of late, the market has been loaded with a variety of period tracking apps such as Clue, Glow and My Calendar none of them provide accurate data. Period sync might happen only due to laws of probability rather than science. For instance, you have periods for 1 week of the month and you live with four other friends the odds are that at least two of you will have your period at the same time. Living with someone for a year or so can make you experience a sync in period cycles only due to mathematical calculations and there is nothing more to this. While you might feel extremely close with your roommate or bestie as you experience period cycles too together it is nothing more than mere coincidence.
Why the Myth of Period Syncing Wont Go Away: https://www.theatlantic.com/family/archive/2019/09/period-syncing-almost-definitely-isnt-real/598714/
The Myth of Period Syncing: https://www.nytimes.com/2019/06/06/well/the-myth-of-period-syncing.html
Women who Spend More Time Together End Up Having Periods at the Same Time. Myth or Fact? https://timesofindia.indiatimes.com/life-style/health-fitness/health-news/women-who-spend-more-time-together-end-up-having-periods-at-the-same-time-myth-or-fact/photostory/71292326.cms
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Dietitian & Nutritionist Dr. Nafeesa Imteyaz.