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New study debunks the myth of women’s monthly “brain fog”


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Monica Costa - published on 08/23/17

Turns out menstruation doesn't affect a woman's cognitive abilities

Menstruation (from the Latin mensis, or month) is a natural part of the monthly cycle for the vast majority of women, but it has long been enveloped in mystery and myth. In many cases, traditions have been built around it, generally in ways very undignified to women.

Many ancient cultures considered women unclean during their period. Some of them even built huts outside the village to house them. In the Old Testament, it was considered a sin for a woman to enter the temple during her period. In some villages in China, to give another example, people believed that menstrual blood could not touch the ground in order not to offend Mother Earth.

Smiling Woman

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But even closer to home, there is another myth that has been going around for centuries. Who has not heard sayings about how a woman is just “off” because she’s “hormonal” or “PMSing”? There’s rarely a direct reference to menstruation, as it is still considered dirty and taboo. There are prejudices that say that during menstruation women become dumber, or that hormonal changes “reduce” a woman’s cognitive abilities. And this idea has been repeated to us so often that we may even begin to believe it’s true.

Working memory and attention span

Nothing is further from the truth, according to a study by researchers at the University Hospital of Zurich, who published their findings in the magazine Frontiers in Behavioral Neuroscience. The study shows that hormonal changes during the menstrual cycle do not affect women’s cognitive ability.

The study monitored 68 German and Swiss women during two menstrual cycles and tested them on various cognitive functions: working memory (i.e., the short-term memory required to perform tasks or process information), cognitive bias, verbal fluency, and attention span for performing two tasks at the same time.


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During each menstrual cycle, the tests were done four times during moments when the subjects’ estrogen, progesterone, and testosterone levels were different. The result was clear: no cognitive functions were affected by the rise and fall of hormones.

Myth busters

The lead researcher, Prof. Brigitte Leeners, explained that she started the study precisely to rule out a recurring perception in her work — that menstruation affects women’s brains — and to be able to give an answer to those women who have this impression.

While the research is positive, Leeners does say that more studies with larger sample sizes still need to be done. But in the meantime, this study certainly does debunk previous findings — often based on even smaller sample sizes of ten or a dozen — that found false correlations between menstrual periods and brain fog.

This article was originally published in the Spanish edition of Aleteia and has been translated and/or adapted here for English speaking readers.

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