Image: Friends
A lot of funny things can happen when you live or work with a bunch of other women. You might start talking or even dressing alike, and you definitely get acquainted with one another’s weird habits.
But despite the urban myths you’ve heard, you won’t necessarily share a menstrual cycle.
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Sure, the idea of being so close to your friends that your bodies team up in solidarity once a month is kind of cool, and you’ve probably heard of it happening to friends of your friends who lived together.
But according to Dr Ginni Mansberg, it's not something that inevitably happens. Sorry. "I am a bit of a sceptic. It has been noted that this sort of thing can happen, however there's no real biochemical explanation for it and there's no real reason why this sort of thing should happen," Dr Mansberg says.
"In terms of do the hormones that stimulate your ovaries and do you bleed them out into some kind of ether cloud that makes a hormonal aura around you that infects other people... that's not plausible from a biochemical point of view."
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The period synchronisation debate has been around for decades now. It kicked off back in 1971 when Martha McClintock published a study of young women living together in college dorms. Her findings suggested regular interaction with other women could have a "strong effect on the menstrual cycle", a phenomenon that came to be nicknamed 'the McClintock effect'.
However this research, and a number of further studies that attempted to replicate it, has been fiercely contested by health researchers in the years since. As with almost any phenomenon, there is anecdotal evidence that women who work or live in close proximity can (and have) experienced overlapping periods, but Dr Mansberg says there's a simple explanation for that: statistics.
"Here's what I think is going on: over any four week period, 25 per cent of women are having their periods. Some women will overlap during that time - say two out of those seven days with a colleague, and another colleague might share two of those seven days at the other end," Dr Mansberg.
"You can see that statistically, it's reasonably likely that any given time a reasonable number of women who work together or live in a house together will have periods at the same time."
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It's also very possible that because we've heard so much chatter about this mythical menstrual overlapping, we actively search for evidence that it's true and happening to us. Women don't let other women suffer through cramps alone, right? Sisterhood! Solidarity! And so on.
"Because people are aware of this phenomenon, there is a bit of confirmation bias. So when anybody's pulled out a tampon and gone to the toilet during your menstrual cycle you'll go, 'Ah! You see, I told you, I knew it!' but you won't know this until the other girl pulls out a tampon," Dr Mansberg explains.
The concept of having your body sync up with your closest friends' is appealing for some because it seems a little magical - it suggests we don't have control over everything in our lives, or that destiny or some other great force has intervened. If that's what you want to believe, there's no harm in it, just know there's just not a lot of scientific evidence to back it up.
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"I think people are often looking for supernatural explanations for natural phenomena," Dr Mansberg says. "It is an appealing thought, but it doesn't work - your hormones pretty much stay inside your body. You don't have an hormone aura that follows you around and starts penetrating other people."
So the takeaway of all this is: yes, your periods might happen to overlap with the women you spend the most time with. But if they don't, Dr Mansberg stresses there's no need to freak out about the state of your friendship.
"If anyone out there's thinking, 'But I didn't get into the period group! I'm not in sync with my colleagues! I mustn't be in their energy field!' I would take comfort in that it probably doesn't exist. Don't worry about it. Your period's fine."
Has this ever happened to you?