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the claim

Pheromones can synchronize menstrual cycles among women living together

the verdict
CONTESTED
contested - evenly split
Recorded sources
2 sources for · 2 against

Counts group repeated records of the same source within each side. They do not measure evidence strength or source independence.

Is it true that Pheromones can synchronize menstrual cycles among women living together?

Partly. While some observational studies report that women living together experience menstrual cycle synchronization, broader reviews and critiques in human chemical communication note a lack of robust bioassay-led evidence and methodological flaws, leaving the pheromonal basis of the phenomenon heavily contested.

Verdict: CONTESTED · 2 sources for, 2 against · Last checked

The analysis

The claim that pheromones synchronize menstrual cycles among women is a specific, empirical hypothesis that has a long history in both positive observational studies (e.g., McClintock-style observations, represented here by papers [3] and [11]) and severe methodological critiques (papers [1] and [4]). Modern reviews point out that human pheromone claims often suffer from small sample sizes, methodological artifacts, and lack of rigorous bioassay confirmation. Therefore, while some small-scale studies report the phenomenon, the broader scientific consensus views human pheromone-mediated menstrual synchrony as highly contested or potentially artifactual.

The evidence we hold leans evenly split

How this was weighed

official record 3x · fact-check 2x · hedged 1x · crowd & reference 1x

  • Environmental influences cause menstrual synchrony, not pher · peer-reviewed · supports · weight 1.3 · 1989
  • Study of menstrual cycle synchrony in female medical student · peer-reviewed · supports · weight 1.05 · 2023
  • The search for human pheromones: the lost decades and the ne · peer-reviewed · refutes · weight 1.6 · 2015
  • Reproducible research into human chemical communication by c · peer-reviewed · refutes · weight 1.3 · 2020
Evidence for · 2
Environmental influences cause menstrual synchrony, not pheromones
1989
This study observed that women living in close proximity experienced an alignment in their menstrual cycle onset dates over time.
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Little, B. B., Guzick, D. S., Malina, R. M., & Ferreina, M. D. R. (1989). Environmental influences cause menstrual synchrony, not pheromones. doi.org. https://doi.org/10.1002/ajhb.1310010110

Evidence against · 2
The search for human pheromones: the lost decades and the necessity of returning to first principles.
2015
This review highlights that despite claims regarding human chemical communication and putative pheromones, robust bioassay-led evidence is lacking.
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TD, W. (2015). The search for human pheromones: the lost decades and the necessity of returning to first principles.. doi.org. https://doi.org/10.1098/rspb.2014.2994

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More for · 1
Study of menstrual cycle synchrony in female medical students sharing common accommodation.
2023
This prospective study of roommates found statistically significant menstrual cycle synchronization among female medical students sharing living quarters.
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NI, S., S, C., SA, K., S, B., & PK, M. (2023). Study of menstrual cycle synchrony in female medical students sharing common accommodation.. doi.org. https://doi.org/10.4103/jfmpc.jfmpc_382_23

More against · 1
Reproducible research into human chemical communication by cues and pheromones: learning from psychology's renaissance.
2020
This paper notes that studies on human olfactory cues and putative pheromones suffer from small sample sizes and are likely false positives related to the reproducibility crisis.
Get citation
TD, W. (2020). Reproducible research into human chemical communication by cues and pheromones: learning from psychology's renaissance.. doi.org. https://doi.org/10.1098/rstb.2019.0262

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first checked04 Aug 2026
judged → CONTESTED · 3704 Aug 2026
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