4. Periods Sync

Busting the myth: Do periods sync?

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4. Periods Sync

Busting the myth: Do periods sync?

Menstrual synchrony
Menstrual synchrony, the idea that women's menstrual cycles align when living together, is a myth.
Research: Early studies suggested possible cycle alignment due to pheromones or social factors, but they were criticized for poor methodology. Large, well-designed studies find no evidence that menstrual cycles synchronize, suggesting perceived alignment is due to random overlaps from natural cycle variability (21-35 days).
Doc’s Opinion: Doctors generally view menstrual synchrony as a myth, with no solid evidence supporting actual cycle alignment.
Link to details & sources:

Long -form Answer

While some research is conflicting, most evidence suggests that period syncing is a myth.

What studies say:

Early studies suggest pheromones or social interaction might influence cycles, but they’re criticized for small samples, poor controls, and assuming fixed cycle lengths.

Reference: MCCLINTOCK, M. Menstrual Synchrony and Suppression. Nature 229, 244–245 (1971). https://doi.org/10.1038/229244a0

Larger, longer-term studies (e.g., Yang & Schank, 2006) argue synchrony is a myth, driven by chance overlaps due to cycle variability (21-35 days is normal).

Reference: Yang Z, Schank JC. Women do not synchronize their menstrual cycles. Hum Nat. 2006 Dec;17(4):433-47. doi: 10.1007/s12110-006-1005-z. PMID: 26181612.

Research on menstrual synchrony shows mixed results. While some studies suggest positive outcomes, they often suffer from poor methodology and small sample sizes. Larger studies, however, do not support the occurrence of menstrual synchrony and these are supported by larger rigorous stats (bootstrap, Monte Carlo), large sample, long duration.

Hence further research is needed to determine if cycles actually synchronize.

Doctor's opinion:
Despite its popularity, science refutes menstrual synchrony. The "menstrual synchrony" theory was first proposed in the 1970s, but follow-up studies have failed to prove it. What appears like syncing is usually just overlapping cycles due to natural variability of cycle length

Previous3. Exercise worsens period cramps

Last updated 1 month ago

Was this helpful?

Menstrual synchrony
Menstrual synchrony, the idea that women's menstrual cycles align when living together, is a myth.
Research: Early studies suggested possible cycle alignment due to pheromones or social factors, but they were criticized for poor methodology. Large, well-designed studies find no evidence that menstrual cycles synchronize, suggesting perceived alignment is due to random overlaps from natural cycle variability (21-35 days).
Doc’s Opinion: Doctors generally view menstrual synchrony as a myth, with no solid evidence supporting actual cycle alignment.
Link to details & sources:

Long -form Answer

While some research is conflicting, most evidence suggests that period syncing is a myth.

What studies say:

Early studies suggest pheromones or social interaction might influence cycles, but they’re criticized for small samples, poor controls, and assuming fixed cycle lengths.

Reference: MCCLINTOCK, M. Menstrual Synchrony and Suppression. Nature 229, 244–245 (1971). https://doi.org/10.1038/229244a0

Larger, longer-term studies (e.g., Yang & Schank, 2006) argue synchrony is a myth, driven by chance overlaps due to cycle variability (21-35 days is normal).

Reference: Yang Z, Schank JC. Women do not synchronize their menstrual cycles. Hum Nat. 2006 Dec;17(4):433-47. doi: 10.1007/s12110-006-1005-z. PMID: 26181612.

Research on menstrual synchrony shows mixed results. While some studies suggest positive outcomes, they often suffer from poor methodology and small sample sizes. Larger studies, however, do not support the occurrence of menstrual synchrony and these are supported by larger rigorous stats (bootstrap, Monte Carlo), large sample, long duration.

Hence further research is needed to determine if cycles actually synchronize.

Doctor's opinion:
Despite its popularity, science refutes menstrual synchrony. The "menstrual synchrony" theory was first proposed in the 1970s, but follow-up studies have failed to prove it. What appears like syncing is usually just overlapping cycles due to natural variability of cycle length