My friends and I get our periods at the same time, why?

Mothers and daughters, sisters, friends, roommates… There are a million possible combinations, but the fact is that we have all experienced it at some point. Your period comes and that same day you run into another girl or woman (and maybe even several) close to you and he tells you that she has also just had a drop. “How is it possible? Do the rules sync? “, you ask yourself.

By some strange unknown factor, you suddenly find yourself sharing painkillers, tubs of chocolate ice cream and tampons and pads with someone else. But why does it happen?

The truth is that the explanation of this event or anecdote is not entirely clear. There are two theories that seem to argue why you and all your friends get your period at the same time. Throughout this article we are going to tell you about both so that you can decide for yourself which of them makes the most sense. Very attentive!

Why do my friends and I get our periods in sync?

Pheromones, the first culprit for the synchronization of menstruation

  • This theory was promoted by the scientist Barbara McClintock. Barbara began to investigate this strange phenomenon after realizing that the menstruation of seven lifeguards who worked together for an entire summer was synchronized, that is, they all had their periods on the same day or at the same time. After discarding several possible hypotheses, she concluded that the culprits of this event are pheromones.
  • Pheromones are a set of chemical substances that living beings secrete in order to provoke some type of reaction or response in other individuals. Humans also secrete this series of substances and, despite the fact that our sense of smell is not capable of detecting them, the truth is that our brain does perceive and interpret them in the same way that other animals do.
  • In this way, when women release pheromones through urine or sweat, they are recognized by other women close to us (be it our mother, our cousin or our best friend), affecting the levels of luteinizing hormone (LH), one of the main stimulators of ovulation.
  • Although it is a highly defended theory, the truth is that it is not 100% known how pheromones can affect LH, so it is necessary to weigh other alternatives. So much so that many scientists consider that this analysis is full of statistical and methodological errors and that, therefore, it should not be taken into account.

Melatonin, the second culprit in menstruation synchronization

  1. Melatonin is a hormone that is best known for being one of the indicators of circadian cycles. This is so as a consequence of the changes produced in its concentration throughout the day, which notify our brain of the moment of the day in which we find ourselves and whether, therefore, it should increase or reduce its activity.
  2. On the other hand, melatonin also has an essential role in the control of gonadotropin-releasing hormone (GnRH), which secretes FSH and LH, two hormones of great importance during the menstrual cycle.
  3. Thus, if two women perform the same job (as is the case with McClintock’s seven lifeguards), live together, or have a very similar daily routine, with similar light exposure, synchronizing GnRH production, chances are they end up having their periods at the same time.
  4. Some scientists also do not agree with this theory and think that it is a mere coincidence. The truth is that there may be other explanations beyond pheromones and melatonin, such as several girls following similar diets, taking the birth control pill at the same time, sharing exercise routines, having sleep cycles similar/wakefulness or who are experiencing stressors. All this can decisively influence menstrual habits.
  5. Be that as it may, and while scientists continue to search for an explanation as to why our periods come at the same time as our friends, we will continue to share menstrual cramps and possibly be the occasional treat in the form of sweets. Do you sign up?

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