Menstruation does not affect women’s brains contrary to claims that it reduces the ability to think clearly, according to new research.

A team of scientists tested three major aspects of cognitive function in 88 women and found they were not affected by the hormonal changes involved.

The researchers said supposed evidence of poorer performance in tests were likely to have been “false positives” with some studies having fewer than 10 subjects.

Professor Brigitte Leeners, of University Hospital Zurich, who led the new study, said: “As a specialist in reproductive medicine and a psychotherapist, I deal with many women who have the impression that the menstrual cycle influences their well-being and cognitive performance.

“The hormonal changes related to the menstrual cycle do not show any association with cognitive performance.

“Although there might be individual exceptions, women’s cognitive performance is in general not disturbed by hormonal changes occurring with the menstrual cycle.”

The researchers tested working memory, attention and cognitive bias in the group of 88 women and then re-tested 68 of them during a second menstrual cycle.

Writing in the journal Frontiers in Behavioural Neuroscience, they said: “Our results indicate that the literature on associations between hormonal changes during the menstrual cycle and cognitive functioning is prone to inflated effect sizes and probable false positive findings due to methodological biases and random variance.

“In the present study we found no consistent and meaningful associations between prefrontal cognitive functioning and fluctuations in hormone levels that replicated across two menstrual cycles.”

There have been suggestions that period pain has a negative effect on the brain.

Other studies have found that visuospatial tasks were improved during menstrual phases with low oestrogen and/or progesterone.

While the researchers criticised other studies for having small sample sizes, they also said it would be “preferable” to have more than 100 test subjects because hormones can vary at different times.