Think your period syncs up with your housemates'? Here's the science behind it 2 years ago

Think your period syncs up with your housemates'? Here's the science behind it

Ever found yourself on your period at the exact same time as the rest of your housemates?


It’s not uncommon ladies. Running out of loo roll that bit quicker, tampons flying about the place and an excess of 'period pants’ going through the wash. We know all too well...

But does being surrounded by other women really cause our periods to sync up?

Okay, so we've done some searching and well, please try to bear with us here…

In 1971, a study by Harvard researcher Martha K McClintock, alleged that the ‘synchrony and suppression among a group of women (she tested 135) living together in a college dormitory suggests that social interaction can have a strong effect on the menstrual cycle.’

The study also suggested that this synchronising was to prevent one dominant male from reproducing with all the females - they'd have their period at the same time and so they'd be fertile at the same time. Therefore one dominant male wouldn't be able to reproduce with all females.

The study also suggested that pheromones caused this to happen - a pheromone being a type of hormone that affects the behaviour of others within the same species.


But since then, experts have been rather divided, firstly, because not everyone is sure if pheromones even exist in humans, and secondly, because the above research had a few little holes in it and it can’t be replicated either. In the science world, being able to recreate the same experiment it pretty key.

With around half the studies conducted in this area finding no evidence of synchronicity among female cycles, it can sound a bit confusing as to how researchers are conducting these tests. How can they differ so much?

Another study, carried out by researchers in 2012, looked at baboons (I will be their test subject if they really want to test women's cycles. For the love of god, come on.) They created two models - one would look at McClintock’s theory above, while the other would look at the possibility that it's all just down to ‘chance.’

They decided after a few years of research that 'chance' was the most likely. (Boring and less exciting, for sure.)

A researcher and former colleague of McClintock named Jeffrey Schank gave his thoughts and evidence to the Scientific American (a mag dedicated to the latest advances in science). Stemming from his own research, he said the pheromones theory (tested on mice) didn’t work and that there was no evidence of pheromones affecting ovulation. (Science has yet to find direct evidence that pheromones really do exist in humans because a behavioural response [which they should cause] can’t be consistently found in others.)


Schank maintains that due to the length of our cycles and the fact that ovulation and menstruation occur at different times for different women would mean that eventually, an overlap would occur, and our cycles would catch up with one another.

He and his team saw this same overlap in a study looking at 186 female Chinese students living together in a dorm for one year. They didn't find that they were synching with one another.

So, the theories differ. And there's no doubt the realm of ovulation, menstruation and women’s health needs a whole lot more exploration. There are a million and one questions we could ask about all the above (and the heaps of other experiments out there).


In truth, there’s still so much more that needs to be done and even then, we’ll probably never have a definitive, definite, absolute answer. Well, maybe someday.

Until then, we might just have to experiment with our roomies. (LOLLLLL.)

For the month of February, we're #OnTheRag here at Her.


We'll be chatting all things periods, products, and pain as we delve deep inside the uterus to figure out why we bleed and - more importantly - how we cope.

We'll also be talking to the experts about some of the period related conditions you have heard of, plus some of the ones you haven't.

You can follow the rest of the #OnTheRag series here or follow our Instagram account for more period related content.

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