Menstrual cycle and lunar cycle, full moon periods: what are the effects of the moon on our periods?

The word "menstruation" comes from the Greek mene ("moon"), highlighting an ancient symbolic connection. While the average length of the menstrual cycle (29.3 days) is close to that of the lunar cycle (29.5 days), science has found no proven link between Earth's satellite and our biological clock. Still, let's take a closer look at these old beliefs and well-rooted myths.

Since ancient times, the moon has symbolized femininity (Selene in Greece, Mama Quilla among the Incas). Old theories connected lunar phases with the female cycle (full moon = ovulation), but these links are symbolic, not scientific.

For centuries, the connection between the lunar cycle and the menstrual cycle has fueled scientific debate and popular beliefs. While some recent studies suggest a weak but significant influence, there is no proof of universal synchronization. Science continues to explore these connections by comparing biological data and statistical observations.

Research on this topic dates back to the 20th century. Some studies have found correlations, while others have not. This disagreement explains why the debate continues. The similarity in average durations (29.3 days for the menstrual cycle, 29.5 days for the lunar cycle) has long fueled the idea of synchronization. However, the biological mechanisms remain poorly understood.

A study published in 2024 in Science Advances by Prof. René Ecochard and his team analyzed 26,912 cycles from 2,303 European women and 4,786 cycles from 721 North American women. This extensive research reveals that the menstrual cycle is regulated by an internal biological clock that is sensitive to light, just like our circadian rhythm. According to a statement from Inserm: "The menstrual cycle is weakly but significantly influenced by the lunar cycle, suggesting that menstrual regularity is modulated by the moon."

This lunar “modulator” doesn’t mean total dependence, but occasional interaction. The data show geographic differences: European women tend to start their cycle during the waxing phase, North American women at the full moon. These findings still need to be confirmed with larger samples.

If the moon dictated periods, all women would have cycles in sync, which isn’t the case. A statistical study shows that about 50% of women may see their cycle coincide with a lunar phase within ±3 days. This statistical coincidence is due to the similarity in average durations, not a biological connection.

Modern disruptions like artificial light, lifestyle, or stress can throw off your internal clock and make your cycles more unpredictable. Irregular periods have become common, hiding any potential lunar influence. Science remains cautious: the mechanisms are complex, and current studies don’t support a definitive link.

The full moon is often seen as a phenomenon that amplifies emotions and physical states. Don’t we all sleep a little less during the full moon?

If a woman is experiencing premenstrual syndrome (PMS) or is on her period at that time, her symptoms may feel more intense. It’s not the moon causing these emotions, but it can highlight what’s already there.

These effects vary from person to person. A study of 5,800 children found a slight reduction in sleep (-1%) during a full moon, but the impact remains marginally significant. In short, while the coincidence may seem striking, it’s more about personal perception than a proven scientific link.

By combining these practices with actively listening to your body, you can turn every cycle into a moment of well-being. These simple rituals help you build independence and balance month after month.

The link between the menstrual cycle and the lunar cycle is a deeply rooted historical belief. Even though the word “menstruation” comes from the word “moon,” there’s no scientific evidence for a universal synchronization.

A recent study (Prof. Ecochard, 2024) mentions a "weak but significant" influence of the moon on the internal biological clock, but the data remains inconclusive. An analysis by Clue of 7.5 million cycles found no correlation.

Statistically, one in two women may see their period coincide with the moon within three days—purely by chance. The similar lengths (about 29 days) and phases (full/new moon; period/ovulation) reinforce the idea of coincidence, not causation.
The myth persists due to symbolic heritage and the impact of light on our rhythms. In the past, moonlight could have influenced more regular cycles in the absence of artificial lighting.

The full moon doesn’t trigger your period, but it can amplify emotions or existing symptoms. Regardless of any connection to the moon, what matters most is listening to your body and nurturing a kind relationship with yourself. True synchronization comes from tuning in to your own rhythm.