Slide 1: Question: Is there truth in the commonly-endorsed phenomenon of menstrual synchrony?

Slide 2: Answer: Likely not!

Slide 3: Anecdotes about women living together having synchronized menstrual cycles are common, with 80% of women reporting a belief in menstrual synchrony. Pheromones are often cites as the driver of this phenomenon.

Slide 4: In the 1970s, a landmark report by McClintock in Nature reported that women who were close friends roommates in a dormitory had closer onset of menstrual cycles than random pairs. Additionally, exposure to men appeared to be associated with reduced cycle length.

Slide 5: Subsequent analyses have questions the results of the initial report, citing recall bias, short observation intervals, and inappropriate statistics resulting from double-counting of subjects.

Slide 6: Studies in similar population in the ensuing decade have failed to replicate McClintock’s report. Ultimately, this appears to be a case of anecdotal inertia perpetuated by salience bias, causing women to remember temporary convergence cycles during normal variation.


  • McClintock MK. Menstrual synchorony and suppression. Nature. 1971 Jan 22;229(5282):244-5. PMID 4994256.
  • Yang Z, Schank JC. Women do not synchronize their menstrual cycles. Hum Nat. 2006 Dec;17(4):433-47. PMID 26181612.
  • Ziomkiewicz A. Menstrual synchrony: Fact or artifact? Hum Nat. 2006 Dec;17(4):419-32. PMID 26181611.

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