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ninjacolin's avatar

What causes womens' menstruation cycles to sync up?

Asked by ninjacolin (14243points) October 7th, 2013
15 responses
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janbb's avatar

It’s not a proven fact that it does, I believe.

glacial's avatar

Different women have cycles of different lengths. Put in the same place for several months, several women may therefore have periods that coincide. It is just as inevitable that they will then go out of synch. The “synching” notion has been pretty thoroughly debunked, although there are always some who have anecdotal evidence.

gailcalled's avatar

I have never seen this happen in any demonstrable way, either at years at an all-girls’ summer camp or at an all-women’s college.

AshLeigh's avatar

It doesn’t…

KNOWITALL's avatar

Armpits/ pheromones. That’s the folk lore.

JLeslie's avatar

I don’t think it really happens either, but I still have friends who believe it to be true and say they cycled in sync with college roomates. My girlfriend said that she thinks she and her daughter are possibly getting into sync, her daughter started menstruating 6 months ago, and has been every 23 days! God that sucks for a young girl. I’m thinking if one is 23 and the other 28, eventually they will appear to sync for a few months, and then get out of sync again for obvious mathematical reasons.

The thought was pheromones I think. That pheromones from a women you spend a lot of time with would influence your own hormones.

I’m just thinking It doesn’t make sense in nature. A man can make a lot more babies if his harem is ovulating at different times during the month.

I once heard men help keep women regular. That being around testosterone keeps women cycling well. That sounds like a loud of crap to me too.

zenvelo's avatar

It supposedly happened at sororities when I was in college, but realistically that would mean a whole house would be out of circulation at the same time. Anecdotal, not proven.

When the US Agency for International Development first started giving out the Pill in Pakistan in the 1970s, they taught women to take a week off the Pill at the New Moon. So huge swathes of Pakistani were all menstruating at the same time.

Rarebear's avatar

Confirmation bias.

trailsillustrated's avatar

It is true. It is an olfactory response. It occurs with room mates and women living in close circumstances.

JLeslie's avatar

This says it isn’t true. That there was a study saying cycles did sync up, but in the end science has never been able to replicate the results and the first study when analyzed was supposedly not set up well.

trailsillustrated's avatar

^ there you go. It is most definitely true- it is an olfactory response related to the thymus gland. It is only true of women in close quarters, such as sharing a home, showers, etc. Not populations in dorms or stuff like that.

glacial's avatar

@trailsillustrated Huh? The link that @JLeslie provided indicates that it is not actually true, and that it’s just a popular misconception.

ninjacolin's avatar

I personally doubt it’s true myself but the discussion came about when two females who have become fast friends and who just started working together 2 months ago sure enough have both got their periods early at the same day within minutes eachother.

My first reaction was: yea, I think women have odd enough cycles that they MUST sync up every now and then just by chance, The coincidence however is just too intriguing not to share and discuss. So of course syncing periods gets more press than non syncing periods.. so, voila a myth is born.

Still, I promised to try to look it up and I thought I’d ask you guys and see if you knew of any studies etc. Unfortunately, not much to find on the matter. So, I still think it’s a myth.

JLeslie's avatar

@ninjacolin Even being “regular” they can sync up. If one woman’s regular cycle is 28 and the other is 26, eventually they will seem to sync. My period was 7 days long most of my adult life, so even if we did not start same day, my period had a good chance of going on while my friends were menstruating also. I only started early one time in my entire life of menstruating. I would think if girls are very irregular even if there is any truth to syncing it would wreak havoc on trying to sync. People who miss periods have their hormones all whacky usually.

@trailsillustrated You read it wrong. It looks like periods syncing is as true as vitamin C curing colds.

glacial's avatar

Here’s an article to get you started, @ninjacolin.

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