Do women who live together get their periods at the same time, and if so, why? Does the moon have anything to do with periods?
Regarding menstual cycle synchrony, Cecil’s 1986 article says yes, but his 2002 article says maybe not.
As for the link between the moon and menstrual cycle, Cecil says no.
The moon part was discussed at great length a month ago in Menstruation and the moon. Short answer: No.
The moon just gets involved because its period coincides (somewhat) with your average human female period. But other animals have very different period lengths.
As for women getting in synch with each other, Pepper Mill has no doubt that this is true. She had extremely irregular periods, and the women in her social circle ended up with irregular cycles that were in synch with hers (she’s evidently an alpha female in this regard), and they all blamed her for it. She ended up on birth control pills for several years simply to “even out” her cycle. Her friends were grateful.
Cecil may say no, or maybe not, but here’s an area where I’m still unconvinced. But I haven’t done any in-depth studies or anything. Just my personal experiences.