Science has confirmed what women have long known
Scientists long debated it: is it true that the menstrual cycle synchronizes with the lunar one? In 2021, the neurobiologist Charlotte Helfrich-Förster and her colleagues published, in Science Advances, an analysis of women's long-term menstrual records.
The conclusion was unexpected even to the authors themselves: in women with a cycle longer than 27 days, menstruation periodically synchronized with the lunar phases — with both the moon's cycle of illumination and its gravitational cycle.
But here is the detail that changes everything: with age, and under exposure to artificial light at night, this synchronization disappeared. Cycles grew shorter and lost their tie to the moon. In 2024 this was confirmed in a sample of 3,000 women. Three independent studies — the same result.
Sources
- Helfrich-Förster C, Monecke S, Spiousas I et al. Women temporarily synchronize their menstrual cycles with the luminance and gravimetric cycles of the Moon. Science Advances, 2021; 7: eabe1358. doi: 10.1126/sciadv.abe1358
- Ecochard R, Stanford JB, Fehring RJ et al. Evidence that the woman’s ovarian cycle is driven by an internal circamonthly timing system. Science Advances, 2024; 10(15):eadg9646. doi: 10.1126/sciadv.adg9646
- Helfrich-Förster C, Domenie ED, Mitesser O et al. Synchronization of women’s menstruation with the Moon has decreased but remains detectable when gravitational pull is strong. Science Advances, 2025; 11(39):eadw4096. doi: 10.1126/sciadv.adw4096