Truth or Old Wives Tale: Do Women's Periods Really Sync Up?

Periods. For some of us, we look at them as the thing that sits at the end of a sentence. For about half of all women in America, a period is a very different but very normal part of life—and while it certainly punctuates life, it's not something you'll often see in a sentence.

Menstruation is something that's seldom spoken of out in the community—when's the last time you heard someone talk about it with friends? As a result of this stigmatization, it's not unusual for old wives' tales to make their way into what people think they know about periods—and often, these misconceptions don't get debunked until much later in life.

For graduate nurses, such as those who have completed an online ABSN program, dispelling myths about women's periods is an important pathway to ensuring that women are supported with accurate and reliable medical advice. Let's dive into a common myth about periods—the notion that women's periods sync up—and explore how it became such a widespread myth.

We Don't Talk About Periods Enough

When was the last time you talked about periods? For many people, menstrual health is not a conversation topic that's brought up widely—often, there's a negative stigma or perception associated with talking about periods.

In reality, periods are just a normal part of life. The average woman will typically have periods, roughly once every four to five weeks, for about forty years—up until menopause. That can sometimes come with medical complications—for example, it's estimated that roughly 10% of women suffer from endometriosis.

Movements across the world are beginning to normalize the conversation around periods and menstruation. For example, May 28 marks Menstrual Hygiene Day, a movement that brings together people from both the public and private sectors to raise awareness about the need for education and information about menstrual health.

In part, not talking about the realities of periods can often result in misinformation and myths spreading. Hopefully, campaigns such as Menstrual Hygiene Day will help to raise awareness and foster positive change.

The McClintock Effect

One of the earliest references to syncing periods is an article published in the early 1970s by researcher Martha K McClintock. The entry, published in Nature in 1971, conducted a study on 135 college students who lived together and suggested that pheromones or other social factors may play a role in synchronizing menstrual cycles.

When research is published, it often becomes a focal point for conversation. It's important to know that while research papers are occasionally retracted, they are still relatively rare. As a result, disputed papers often make it to the mainstream of conversations—even if the findings have been debunked or disproven.

A modern example of this so-called McClintock Effect can be seen in contemporary discussions about the relationship between vaccines and autism. In 1998, Andrew Wakefield published a paper in the widely regarded journal The Lancet, which contained significant errors. While this article was retracted and debunked, in the quarter-century since publication, substantial misinformation continues to seep into public conversation.

Modern Data Tells a Different Story

In reality, contemporary analysis of McClintock's research highlights that there were flaws with the methodology and findings of the report. In the half-century since the original Nature publication, much research has been done to attempt to validate McClintock's findings—with studies often discrediting the original findings.

In 2006, a study on 186 women living in a dormitory in China found that any apparent syncing of periods seemed to lie within the realm of mathematical coincidence. Just over a decade later, the advent of smartphones provided further opportunities to research menstruation synchronicity.

In 2018, period tracking app Clue worked in conjunction with Oxford University to research groups of cohabiting individuals. In total, approximately 1,500 users from a mix of different households participated. The findings further dispelled the findings of McClintock's original research.

Why Does the Myth Prevail?

Why does the myth continue to capture the imaginations of the community? As it turns out, we can probably place some of the blame on misinformation and misleading data that can appear at an individual level.

It's important to recognize that everyone's period cycle is different—while they typically occur once every 28–34 days, sometimes they can occur at variable frequencies (and, in some cases, may not appear for a little while).

The resulting irregular cycles can result in points where it appears that periods are lining up—whereas, in reality, it's simply different period cycles overlapping. It's much like the birthday paradox—we have preconceived notions of how something must work, but in reality, the outcome is completely different from what we expect.

Old wives' tales about the menstrual cycle, such as menstrual synchronicity, are an ongoing challenge when talking about periods. As organizations continue to normalize the discussion around periods, we can only hope that this also helps to dispel some of the myths that have engrossed conversations in the past five decades.