Dear Dr. Hypothesis,
I have heard that women who live together tend to menstruate together. I am a girl, and back when I used to live with four other girls I noticed this synchrony effect. Now, I live with just one female flatmate. We both menstruate regularly, but never at the same time. Could it be that a critical number of women must be present in order for the synchrony to start?
Out of Sync
Dear Sister Sync,
The idea that women who spend a lot of time together will menstruate together has carved out a firm place in the annals of dormitory lore, thanks to decades of anecdotal reports from cohabitating women (and their male observers). Still, believe it or not, after almost 40 years scientists have yet to agree on whether the phenomenon constitutes myth or reality. Read more »