Every month, for about two to three days before my period, I experience terrible brain fog. It’s similar to the feeling I get when I oversleep: I can’t think as quickly or clearly as I normally can, my memory is a bit fuzzy, and I’m just kind of out of it. Experts use the term brain fog to describe a range of temporary “cognitive difficulties,” like trouble focusing, forgetfulness, and mild confusion. Brain fog isn’t a medical diagnosis; rather, it’s a symptom associated with a slew of health conditions, including pregnancy, depression, long COVID, and, yes, PMS (premenstrual syndrome). The research on PMS-related brain fog is limited, but anecdotally, going through it can be a slog, Jennifer Roelands, MD, an ob-gyn who specializes in holistic medicine, tells SELF. For example, the mental cloudiness and impaired concentration may hurt your performance at work, as SELF previously reported, and research suggests that PMS symptoms, including cognitive ones like confusion, can also impact personal relationships. For me, the easiest tasks—like sending an email—suddenly feel difficult, and sometimes I feel like I lack the wherewithal to navigate even simple conversations. “To deal with that every single month is pretty miserable, but there are definitely things you can do to help,” says Dr. Roelands. More on that soon, but first… Why might menstruation trigger brain fog?I’ve always chalked premenstrual brain fog up to hormonal fluctuations that occur during my cycle. I figured the mental sludge had something to do with cyclical changes in estrogen and progesterone. That’s possibly not too far off, according to Dr. Roelands. Menstruation can cause all sorts of drastic and rapid hormonal changes that are associated with an array of symptoms (a.k.a. PMS), as SELF previously reported. It’s known that estrogen and progesterone also play a role in brain function and cognition, but how, specifically, changes in those hormones may directly contribute to brain fog is somewhat unclear, Cheruba Prabakar, MD, ob-gyn and chief medical advisor for wellness-ingredient company Purissima, tells SELF. The evidence has been mixed: A small 2017 study concluded that there is no relationship between brain fog and the hormonal changes that take place leading up to menstruation, while a 2020 analysis suggests that it’s just too early to declare, either way, if and how menstrual-related hormone changes impact cognitive functioning. Though the research on PMS and brain fog is inconclusive, many reproductive health specialists, including the ones SELF talked to for this story, say that, anecdotally, people commonly report experiencing brain fog both before and during menstruation. The going theory, according to both Dr. Roelands and Dr. Prabakar: The mentally fuzzy feeling is likely due to all of the significant changes in hormones, neurotransmitters, and insulin levels that happen during your menstrual cycle. And there are some data that support this theory: Research shows that estrogen and progesterone influence neurotransmitters like dopamine and serotonin that deal with executive functions (a group of complex cognitive abilities that includes working memory and problem solving). Studies have also linked low estrogen levels to cognitive impairment and higher estrogen levels to improvements in memory and learning. There are estrogen receptors all over the brain, says Dr. Roelands, so it makes sense why your cognitive function is affected by the estrogen dip that happens during PMS. Experts also know that cognitive issues are common in menopausal people who have chronically low estrogen levels.