Truth or Myth: Is Period Synchronization a Thing?

By Alma Bengio

I’ve always thought it was a thing. I always thought that physical proximity with a friend who was on their period could make my cycle sync with theirs. To be honest, I never had a reason not to believe it. I felt like it did happen, that after having sleepovers with friends or spending long hours with them, I would get my period or we would both get it together.

It’s one of those myths everyone’s always heard about but noone really knows if it’s 100% true... So I’m here to clear that up for you. Period syncing is not a thing. There have, however, been many studies trying to prove it, so your doubts don’t come out of nowhere. It all started in 1971 when Harvard doctor Martha McClintock studied a group of 135 women living in a college dorm. The research proved that period synchronization did increase amongst friends spending the most time together, and roommates. 

McCLintock proposed that when someone becomes aware of somebody else’s period, by seeing them changing pads or tampons, or because they mention it, that person’s period might start too. This notion has become known as the McClintock Effect.

Since this study, the evidence has varied greatly. Some groups of menstruators have synced their cycle, while others have not. It becomes more of a question of chance than actual statistics, meaning there is no real correlation between physical proximity and syncing cycles. 

So no, cycles don’t synchronize. However, if you’ve been living with someone for a year, it is inevitable that eventually you will get your period at the same time. This is just a question of timing however. Regardless, there’s nothing like that feeling of connection when you get your period at the same time as a close friend. It gives you a sense of companionship that is very much appreciated.