Can Women’s Periods Really Sync Up?

When I was in college living with two other women, they swore to me that their periods had shifted to align with my cycle. Up until spending most of their time with me, they’d had their periods at one point in the month and now they were getting theirs when I got mine instead. We decided that our periods had synced up.

Many women have stories like mine, whether it’s with college roommates, close friends or family members. But is syncing up really a thing? Is there actual clinical evidence to suggest that women who spend a lot of time near each other would start to get their periods at the same time? The short answer is maybe — researchers call it “menstrual synchrony.” As of now, there’s no foolproof evidence that it’s a real physiological phenomenon, but there have been a few interesting clues.

What exactly is “menstrual synchrony”?

Menstrual synchrony is a theory that women who live near each other or spend a lot of time together will start to see their cycles sync up so that they get their periods around the same time. Pheromones, or “airborne chemical signals that are released by an individual into the environment and which affect the physiology or behavior of other members of the same species,” have been thought to play a role.

The concept was first documented in Martha McClintock’s seminal research paper in 1971. McClintock observed 135 female Wellesley College students living in the same dorm and found “a significant increase in synchronization of onset dates” among the women who spent a lot of time together. According to these findings, it’s not just an anecdotal phenomenon — women do sync up.

So, can women’s periods really sync up?

While some of the researchers who followed —> Read More