Do women’s periods actually sync up with each other?

Experts unpack the common myth of menstruating people’s cycles synchronizing when they’re in close proximity for long enough

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To be someone who menstruates means continuously trying to untangle fact from fiction. Is it true that you can’t swim on your period? No. Does the scent of a person menstruating attract bears? Also no.

There is one period rumor I’ve always kind of enjoyed, though: when women are in close proximity for long enough, their menstrual cycles will eventually sync up, also known as “menstrual synchrony”. I’ve had several friends over the years claim that my period had yanked them on to my cycle.

Body composition: A high BMI is associated with irregular cycles, says Kling.

Age: “Menses can be irregular in adolescents and as people approach menopause,” says Jensen.

Psychological stress: Depression can disrupt a person’s cycle.

Medication, such as birth control.

Medical conditions, such as thyroid disease, polycystic ovarian syndrome or menopause.

Lifestyle factors, such as smoking, alcohol and caffeine consumption, diet and physical activity.