Current studies suggest that the periods of women living together do not sync up, but the verdict is still out. The popular belief is that by being around someone who is menstruating, their pheromones will influence you and eventually cause your cycles to sync up. This was further supported by a study of 135 university women living in the same dorm by McClintock. However, later studies seem to disprove and prove the theory, so it is difficult to tell.
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