Brain Fog Before My Period: Is It PMS or Something More Serious?

You're not imagining it. You may be more forgetful before your period.

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I seem to get brain fog around my period. Help!

You're not alone: Brain fog is a common symptom experienced by people during their menstrual cycle. That sluggish, cloudy feeling you get in your head when you can't think clearly, forget things, or start making simple mistakes affects everyone differently.

How Do You Know It's Brain Fog?

According to a 2021 study published in the Journal of Psychosocial Nursing and Mental Health Services, brain fog is technically referred to as "cognitive difficulties." Brain fog does not exclusively affect when you are premenstrual, though that is a common time to experience it. The condition can also be a response to lack of sleep, poor nutrition, medications, or drugs. Despite how common it is, a study published in 2013 in Frontiers in Physiology noted that brain fog (which is experienced as slow thinking, difficulty focusing, confusion, lack of concentration, forgetfulness, or haziness in thought) is not fully understood.

Before Your Period

Many people report brain fog, or trouble thinking or focusing, as a symptom just before their period. We can understand this by thinking about how hormones fluctuate during the menstrual cycle. We know that hormones like estrogen and proestrogen seem to influence how the brain functions. In a typical cycle, progesterone levels rise in the two weeks leading up to your period; that has been linked to a drop in serotonin, a neurotransmitter that boosts mood and helps keep you sharp.

In some cases, brain fog is experienced as a symptom of premenstrual dysphoric disorder (PMDD). PMDD is a health problem that takes place in the week or two before your period starts, as hormone levels begin to fall after ovulation. The Office on Women's Health defines PMDD—a condition affecting up to 5% of women of childbearing age—as a condition that causes more severe symptoms than PMS, including severe depression, irritability, and tension.

Unsettled Science

However, the science is still unfolding on the effect of the fluctuating hormones of the menstrual cycle on the brain. A 2107 study published in Frontiers in Behavioral Neuroscience looked at the effects of menstrual cycle hormones and brain functioning. Researchers at University Hospital Zurich in Switzerland followed 68 women over two menstrual cycles and had them complete a series of cognitive tests. At various stages of their cycle, the women's memory, bias, and multitasking skills were tested. The study results showed that changes in hormone levels (estrogen, progesterone and testosterone) were not associated with changes in performance on any of the cognitive tests.

In addition, the authors of a 2020 study published in Brain Science explored the role of sex hormones on cognition during the menstrual cycle. They describe the menstrual cycle as "a convenient model " to look at how changing levels of these hormones can affect the brain and cognitive functioning but concluded that future studies are needed to be clear on the role of sex hormones and brain functioning.

Anemia and Brain Fog

Another cause of brain fog is iron deficiency anemia. Iron deficiency anemia is the most common type of anemia. This condition happens when your body does not make enough healthy red blood cells or the blood cells do not work correctly.

Because iron-deficiency anemia can happen when you lose a lot of blood due to heavy periods, anemia symptoms can appear to be more severe during your period.

According to the Office on Women's Health, iron-deficiency anemia can cause serious health problems if left untreated. With anemia, the heart must work harder to make up for the lack of red blood cells or hemoglobin. This extra work can harm the heart.

Your healthcare provider can check your levels with a quick blood test, and if you're anemic, she'll likely prescribe supplements. It's also a good idea to add more iron-rich foods, such as red meat, leafy greens, egg yolks, and beans, to your plate. Vegetarians are particularly prone because most people get iron from animal products.

Beating the Brain Blahs

If you know you are susceptible to brain fog, take some proactive steps to minimize the symptoms. You can monitor your cycle so you know when you'll be most apt to feel dull. On those days, be diligent about writing things down in your day planner, and prioritize shut-eye even more—getting behind in sleep makes things much worse. With good sleep habits, you should feel more refreshed and sharp.

Health's medical editor, Roshini Rajapaksa, MD, is assistant professor of medicine at the NYU School of Medicine.

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