science of us

The Hazy Science of ‘Period Brain’

Photo: Nick Dolding/Getty Images

A couple of weeks ago, on my way into work, I sailed right past my subway stop. This, in itself, wouldn’t be so outlandish, except that I was looking right at the sign, had plenty of time, and then just … didn’t get off the train. I only processed what had happened halfway to the next stop, at which point I got off and shamefacedly reversed course.

I have my suspicions about what made me do this: namely, I was on my period. For me, this usually means my brain gets fuzzy and everyday words are lost to me, a phenomenon I call “period brain.” I was curious to know whether this was something that happens to other women, though I soon discovered that there is scant scientific evidence. A study published last year, for example, which tested the cognitive capacities of 88 menstruating women, found that there was “no consistent association between women’s hormone levels, in particular estrogen and progesterone, and attention, working memory and cognitive bias.” Though changes in cognitive ability were reported in the first cycle of experimentation, they were not replicated in the second, and researchers suggested that those studies that do suggest a link between menstruation and cognitive change suffer from methodical limitations and/or small sample size.

Even so, I swear this happens to me, and several other women I know. My esteemed colleague Kelly Conaboy compares period brain symptoms to those of having a cold. “I feel like I can’t even look out of my eyes straight because my brain is so foggy,” she says.

“Period brain is so real,” agrees another esteemed colleague, Maddie Aggeler. “I feel fuzzy, like I’m on a 30-second delay all the time. It’s not the PMS thing where I’m super emotional it’s just … slow, like mentally running through sludge. I have 500 similes about it,” she adds.

It’s anecdotal, true, and it certainly doesn’t happen to all women. But it does happen to some of us, and I don’t believe I’m imagining it. But just in case, I reached out to Dr. Jason Kanos, a gynecologist at Mount Sinai in New York, to see if he’d heard of anything like this from his patients. “I’ve definitely had patients who feel that the period or the time right before the period can change the way they think, not only in terms of PMS or feeling moody/irritable, but issues with memory,” Kanos tells me. “For some women, it’s in a more positive sense — more euphoric, or sexier. That’s not common, though.” Ha. Can you imagine.

As far as how period brain might work if it were real, here’s one theory: In 1995, a group of scientists at Umea University in Sweden discovered that certain proteins were activated by estrogen receptors in several areas of the brain connected to thinking, memory, and attention. Because estrogen fluctuates during the menstrual cycle, the scientists reasoned, this could explain why some women complained of “brain fog” during their periods. There is also some evidence that estrogen may affect different women differently depending on their personality, which could be another reason why Kanos says he doesn’t hear cognitive complaints from many of his patients — he guesses around 10 percent. (Maybe it’s because they’re more focused on their debilitating cramps? Just a thought.)

And yet even asking the question about my own experience of “period brain” feels fraught; after all, this is the knee-jerk reasoning of so many misogynists as to why women shouldn’t be in power — we’re “too hormonal.” It’s something the evolutionary scientist Martie Haselton grapples with in her recent book, Hormonal, an overview of her work studying how women’s hormonal cycles may influence their behavior. As she explained in an interview with The Guardian earlier this year:

I get a strong sense that if you ascribe a woman’s behavior to biology, people will automatically think that women are automatons, driven by their hormones and unable to regulate their own behavior. That is false. There is a female stereotype, whereby any time a woman does something a little bit difficult to understand, then it is hormones that make women “irrational.” But nobody says that about men. For that reason, those who are concerned about women achieving equality with men worry that if we talk about women and hormones, then people will say such things as women shouldn’t hold higher office and so on. That’s silly, because men have hormones, too. Our hormones don’t make us crazy, they don’t make us irrational. They nudge us. And to the extent that we understand what those hormonal nudges are, we can exploit them.

And, by the way, men have hormonal cycles, too, which can impact their cognition by increasing impulsivity. Only their cycle happens every day:

Men have daily hormonal cycles. Super-early in the morning, testosterone peaks and then it dives. Testosterone is really important for building male bodies, maintaining muscle mass and their fertility, and so it is important. But it also has its drawbacks. It is associated with increased aggression, more impulsive decision-making and some other things that can get you into a lot of trouble.

In Haselton’s view, then, information about the hormonal cycle is just that: information. And it’s better to know, she writes, because then you can make better choices about your own behavior. “We should become familiar with the potential nudges that affect our behavior,” she writes at the end of her book. “And we should know that choosing to act on those behaviors is an individual choice, dependent upon our own preferences and goals. Being naive to our hormonal natures will not help us. Being hormonally intelligent, on the other hand, will.”

The Hazy Science of ‘Period Brain’