Does Your Period Tend To Sync With Your Friends, Too?

When I was in my undergraduate years, my best friends and I never had trouble keeping track of our periods. We knew that once one of us starts menstruating, we will follow the lead. Like that scene from the, No Strings Attached (2011) when Ashton Kutcher enters the room in the girls’ apartment and looking at them holding hot water bags to their abdomen exclaims “You’re all on the same cycle!”?

In fact, when I told about this weird phenomenon to someone I knew, I was told that it goes on to show the closeness or bond shared among menstruators. I found out quite late that is it popularly known as the McClintock Effect or the phenomenon of menstrual synchrony, an alleged process according to which women (I prefer to think all menstruators) living in close proximity tends to experience the onset of their menstrual cycles at the same time.

The idea has been generated by the pheromone effect. Pheromones are chemicals released by animals that influence the behaviour of others of the same species, and a considerable amount of literature exists to show that among animals and insects, pheromones can affect hormonal behaviours.

However, no existing study of the pheromone effect impacting humans exists to this date. In fact, after the McClintock Effect first came to be widely regarded in 1971, researchers went on to argue about the several methodological flaws in the study itself and 2013 successfully concluded that menstrual synchrony is not likely to exist.

How Credible Are These Theories?

In fact, with the widespread use of period tracking applications, the McClintock conclusion has come to be completely discarded. Researchers have also investigated the lunar phases and their supposed power to push around a menstruator’s period cycle. After all, the menstrual cycle has been traditionally believed to be in sync with the lunar cycle. However, no creditable research has been found to support these old wives’ tales.

Most scientists have shown that one menstruator living with another for a certain long time, then mathematically their period cycles are supposed to coincide a couple of times during the year. Others have shown that people living in close proximity experience the same routines – diet, sleep schedules, exercise and shared stressors – which could possibly have led to a shared menstrual habit as well. However, there are other, more important and scientific things that go on to affect one’s period cycle, like:

1. Birth Control Pills: They alter the levels of estrogen and progesterone and can significantly meddle with one’s menstrual cycle.
2. Stress or Anxiety: Mental Health, especially constant worrying, can lead to fluctuations in one’s period cycle.
3. Chronic Illnesses: If a menstruator is undergoing a certain illness for which they are under medication, then their period cycle might fluctuate. In fact, PCOD is one of the many diseases that sustain irregularity in periods and an inconstant period cycle.
4. Anorexia/Bulimia: Highly restrictive control over calorie intake can also affect one’s period cycle.

BBC News reports Alexandra Alvergne, an associate professor in biocultural anthropology at the University of Oxford saying, “  As humans, we always like exciting stories. We want to explain what we observe by something that is meaningful. And the idea that what we observe is due to chance or randomness is just not as interesting.”

A 2006 study had successfully shown that among 186 women living in groups in a dorm in China, period syncing was merely a mathematical coincidence while a smaller study conducted in 2017 has shown that almost 44% of the participants experienced period syncing, even the common period symptoms like menstrual migraine coincided. Does this then show that menstruators might be influencing each other’s periods in ways beyond the timing of their menstruation? To date, researchers aren’t quite sure.

Menstrual synchrony is and will always be hard to prove because period cycles are not uniform across individuals and populations. They may vary with respect to various irregularities and factors both physical and external. Many popularly believe that the reason menstruators believe in the concept is that they feel comforted to think that someone close to them is undergoing the exact same process and can relate with their mood, cravings and bodily discomfort.

Finally, syncing one’s periods might not have any scientific evidence to back it up but it is absolutely okay to believe in the experience of being on your period and feeling the pre-menstrual syndromes, the skin breakouts and the menstrual cramps, they are your experiences, they are real and never believe anything otherwise.

Written by Ahendrila Goswami