Why Do My Periods Sync with My Friends?

It’s the phenomenon we all know: the old sync up. When you’ve hung out with your bestie so much, you’ve adopted their mannerisms… and their cycle. When you and your sister are arguing more than usual… and both have cramps. When the office or classroom has more spare pads than pens. You get it. But why and how do periods sync? Let’s find out.

The Science Behind Menstrual Syncing

So, why do periods sync? Let’s dive into a few theories.

Thought much about pheromones? They’re kinda like external hormones; chemicals, like sweat or oil, that can influence other people’s feelings or actions. In a 1971 research study by Martha McClintock (fun fact: menstrual syncing is also known as The McClintock Effect!), it was found that when menstruating people are together for long periods (ha), pheromones can sync their cycles. The thing is, this theory has been highly debunked by scientists since, arguing methodological and statistical errors.

Some suggest periods sync because of hormonal fluctuations. Even if your cycle is pretty regular, you’ll probably still experience some irregularity in your lifetime. This could be due to hormonal, health or lifestyle changes. So if you’re living with, or are often surrounded by the same people, you’ll eventually experience overlap and sync up. 

Like Stevie Nicks sang, we’re all ‘sisters of the moon’. Or, that’s what some believe about period syncs. Did you know ‘menstruation’ derives from the Latin and Greek words for ‘moon’ and ‘month’? The correlation between periods and the moon is common across many religions and cultures. For a loooong time, people have believed menstrual cycles link to the lunar cycles. And if we’re all under the same moon, maybe that explains why we sync?

But hey, let this sync in: there’s no concrete conclusion to why periods sync. It’s because pheromones aren’t technically hormones, so they’re harder to study. It’s also because everyone’s cycles are unique, so studying the logistics of cycle length, regularity and syncing can be difficult. 

Why do some people sync, but others don’t?

We can go on and on about how different everyone’s cycles and periods are. Yes, all cycles and periods have the same purpose and function. But while some have heavy flows, others only spot. Some go for pads, others tampons. Some sync, others don’t. What we’re getting at, is some things just are as they are. Call it happenstance.

The closest reason as to why some sync and others don’t, is proximity and pheromones. But again, this isn’t fully backed by evidence, just the most widely-accepted answer to how periods sync. So if you’re wondering why you’re not synced with your mates, maybe it’s a sign to hang out more?

What are the benefits of menstrual syncing?

Proven or not, period syncing has its benefits. You know that universal experience when you and your mate are menstruating? Talking about when your last period was, what pain you have, what choccy you’re craving? Well, that’s called social bonding, and it can really help improve your mood and wellbeing. Another benefit of period syncs is just having some support during that time of the month. Fluctuating hormones, especially with conditions like PMS or PMDD, can bring you down and impact your energy and motivation. Having someone by your side going through the same thing can feel a little less lonely. 
If you’re syncing with your besties, why not host a movie night with BYO heat packs or a chocolate chip baking sesh? 

Well, we didn’t get far in finding an answer - and neither has the science. It’s still somewhat of a mystery why and how periods sync. But proven or not, we reckon the period sync is real. So embrace your (sometimes) mysterious menstrual cycle, and all the unique experiences that come with it!

Love, Libra x

Essity makes no warranties or representations regarding the completeness or accuracy of the information. This information should be used only as a guide and should not be relied upon as a substitute for professional, medical or other health professional advice.