What causes one person's period to "latch on" to another person's?

Question

I "synced up" with my friend's period. What is that caused by? Pheromones? Another molecule or chemical? Thank You!

Answer 1

This is known as the "McClintock Effect." It is still a matter of controversy.

No one, at present, has been able to come up with a definitive explanation for this phenomenon. Dr. McClintock herself suggested the presence of "human pheromones", however the evidence for this, and for menstrual synchrony itself, is still sketchy.

It is possible that it's just a matter of coincidence.

For example, if two women have menstrual cycles of nearly the same length, at a certain point of time, it may appear that their periods are occurring closer and closer together. Then, for a few months or possibly longer, their periods will appear to occur at almost exactly the same time. However if they live together for long enough, their periods will begin to diverge again.

This is similar to the fact, that If you flash a strobe light on a moving fan, and you time the strobe just right, the fan will appear to move very slowly, or stop altogether.

If *four* or more women living together began to synchronize their periods, it would be much harder to explain this as simply a matter of *coincidence*. So there may be something to the McClintock Effect after all.....

Answer 2

Women that are in close and constant contact with each other will often end up "synching" their cycles.
This is attributed to the release of 'ovulation' hormones that can release pheromones that can trigger ovulation in other women.
It doesn't generally happen with just normal daily contact (like at school or work), it takes a lot of close and constant interaction for this to happen.

Answer 3

It doesn't happen. My sister and I never "synchronized". My best friend throughout college (nearly 7 years, including graduate work) never synchronized with me. I now live with my brother and his wife, and we do not synchronize. And I'm not talking of a few days difference: I was offset from all these other women by 1-2 weeks.

One of these days, I would like to sit down and calculate the probabilities involved. I think it really is just a misperception of the coincidence.

Answer 4

I heard that your body gives off hormones and when you're around another girl long enough you start to pick up on her hormones and it causes you to have your periods at the same time.

Answer 5

Girls have this hormone called krazeehoeritrone which causes periods to synch up when girl on girl action is involved. Its fine, your secret is safe as long as you dont say anything else about it. You don't want anyone else to know about that crazy night do you?

Answer 6

pheromones

Answer 7

Because women are freaks of nature and their abnormalities can't be explained by natural science.

Answer 8

We breathe pheremones. We can't necessarily smell them, but we respond to them.

Answer 9

coincidence