Feeling foggy? Don’t blame menstruation, study finds
Dr. Brigitte Leeners frequently sees women convinced fluctuating hormone levels across their menstrual cycles can make them feel mentally foggy and sluggish, like the Pixies song, Where is my mind?
So the expert in women’s reproductive health and her team put dozens of women through a batch of computer-assisted brain tasks at different stages in their cycles, looking for any consistent or meaningful changes in cognitive functioning.
They found none.
Overall, “women’s cognitive performance is in general not disturbed by hormonal changes occurring with the menstrual cycle,” reports Leeners of University Hospital Zurich and lead author of the study published Tuesday in Frontiers in Behavioral Neuroscience.
While some studies have suggested hormonal dips and surges really do affect a woman’s attention and working memory, Leeners suspects those positive findings could simply be down to chance and “utterly small” sample sizes (fewer than 10 women in some highly-cited papers).
A woman’s menstrual cycle is typically 28 days and includes three phases — follicular (before release of the egg), ovulatory (egg release) and luteal (post-egg release, the time between when a woman ovulates and gets her period).
For their study, Leeners and her team recruited 88 women aged 18 to 40. A total of 68 women were re-assessed during a second menstrual cycle. Most similar studies have followed women across only one.
Levels of estrogen, progesterone, testosterone and other hormones were measured at predefined days across the cycles.
The women also completed cognitive tests on a touch screen computer measuring divided attention, visual-spatial working memory (the ability to recall shapes and colours as well as their movements) and cognitive bias, or flaws in judgment or thinking people make when processing information.
While some hormones — progesterone and testosterone — were associated with changes across one cycle in some women, the effects didn’t repeat in the second round, suggesting a learning curve effect, Leeners said. “Once the women had done the test the first time, they were better the next time. You perform better when you know the test,” she said. If it had been down to hormones, the women would have had similar scores in both cycles.
“I think the important thing is that women perform independent from hormonal levels,” Leeners said.
In their paper, she and her colleagues add that “caution is warranted when conclusions are made for specific hormonal effects on cognitive functioning.”
Some courts, for example, have accepted menstrual stress as a mitigating factor in the sentencing of female offenders, the argument being that “women were in their premenstrual phase and so they could not think properly and did things they should not have done,” Leeners said. One American law professor once famously argued premenstrual stress should be considered a form of temporary insanity.
However, according to Leeners, “women’s hormonal-menstrual cycle related changes do not limit them in their cognitive functioning.”
Her team wasn’t studying “premenstrual dysphoric disorder,” a debilitating condition thought to affect two to five per cent of women that can cause severe depression, irritability and mood changes before menstruation.
Also, although their sample was larger than most, it still involved fewer than 100 women. In addition, the researchers assessed only three brain functions, which, they note “are certainly not exhaustive and hence do not cover the whole range of cognitive functioning.”
One study published by British researchers in 2014 found women performed worse on attention-based brain tasks — they were slower and less accurate — when they were experiencing period-related cramping and pain. About one-third of the women in the new study had endometriosis or polycystic ovarian syndrome, which can affect hormone levels. However, the finding held after the researchers controlled for endocrinological problems.