Can A Full Moon Affect Your Menstrual Cycle?
The word menstruation is etymologically related to the word moon (per Online Etymology Dictionary). It makes sense, as both follow a monthly cycle. Some may wonder if the connection goes even deeper than linguistics. Since the moon affects the tides of the Earth, does it also affect the tides of our bodies?
This possibility has fascinated researchers for decades. Scandinavian and American studies in 1986 (via Acta Obstetricia et Gynecologica Scandinavica) and 1987 (via Human Biology) claimed that this is indeed the case, with women being more likely to menstruate around the new or full moon. According to Healthline, a 1977 study suggested that people who got their periods during the new moon were more likely to become pregnant.
A 2021 study published in Science Advances found that 5 of the 8 women surveyed often synced up with the lunar cycle, but that this synchrony was lost as the women became more exposed to artificial light. The study concluded that "in ancient times, human reproductive behavior was synchronous with the moon but that our modern lifestyles have changed reproductive physiology and behavior."
Some studies refute the link between the lunar and menstrual cycle
In the largest study ever conducted on the topic, a 2019 analysis of over 1.5 million users of the menstrual cycle tracking app Clue found no significant link between lunar cycles and periods. Clue observed that the connections found in earlier studies were conflicting and often small. It may be tempting to chalk this up to artificial lighting. However, a 1997 study published in Current Anthropology examined a population with no electrical lighting and also reported no relationship between the lunar cycle and the women's menstrual cycles.
Clue points out that it's statistically likely for some women's cycles to line up with the lunar cycle just by virtue of coincidence. That being said, Clue does acknowledge a potential influence of light upon the menstrual cycle, citing research that mimicking lunar light patterns may improve menstrual cycle regularity.
Healthline notes that regardless of the science, there is nothing wrong with embracing a spiritual link between one's body and the processes of nature, including the cycle of the moon.