“Am I Going Crazy?” The Neurobiology of Brain Fog
Why your midlife memory lapses are a temporary power outage, not early dementia.
It usually happens like this: You walk into the kitchen and stop dead. You have absolutely no idea why you are there. Or you are in a meeting, and a common word—a word you have used a thousand times—vanishes from your brain.
For many of my patients, this isn’t just annoying; it is terrifying. They sit in my office, voice trembling, and whisper the question they are too afraid to ask their partners: “Dr. Amos, is this early Alzheimer’s?”
If this sounds like you, I have good news. You are not going crazy. You are not developing dementia. You are experiencing a very real, measurable, and often temporary neurological event caused by the withdrawal of estrogen.
It Is Not “Just Stress”
For years, women were told their midlife forgetfulness was due to the stress of aging parents, teenage children, or career pressure. While those factors don’t help, we now have imaging proof that something profound is happening inside the skull.
The brain is an energy-hungry organ. It runs on glucose. And for 40 years, estrogen has been a key part of the system that helps your brain cells burn that glucose for energy. Estrogen receptors are densely packed in the hippocampus (memory) and the prefrontal cortex (executive function).
When your estrogen levels crash during perimenopause, your brain essentially faces a “bioenergetic crisis.”
The Data: The “Starving” Brain
We owe a debt of gratitude to neuroscientist Dr. Lisa Mosconi. Her team used PET scans to look at the brains of perimenopausal women. The results were striking.
The scans showed a significant drop in cerebral glucose metabolism—essentially, the brain’s ability to produce energy—during the menopausal transition [1]. In her images, a pre-menopausal brain lights up with activity. A perimenopausal brain looks darker and less active in those key memory centers.
Your brain isn’t broken; it is temporarily starving. It is struggling to function without the fuel additive (estrogen) it has relied on for decades.
The “Dip and Rebound”
Here is the most comforting data I can give you.
The Study of Women’s Health Across the Nation (SWAN) is a massive longitudinal study that followed over 2,000 women as they went through menopause. They tested their cognitive speed and memory repeatedly over years.
The researchers found a distinct pattern: Women experienced a decline in cognitive processing speed and memory during late perimenopause. But here is the key: For many women, this was temporary. Post-menopause, the brain adapted, and cognitive performance often rebounded to pre-menopausal levels [2].
This suggests that “brain fog” is a transition state—a rocky bridge your brain has to cross as it rewires itself to work without high levels of estrogen.
My Advice
Stop Panicking: Anxiety eats up bandwidth your brain desperately needs. Know that this is a physiological phase, not a permanent decline.
Consider MHT: If your brain fog is severe, Menopausal Hormone Therapy (MHT) can help. By restoring estrogen, we can often “turn the lights back on” in those glucose-starved neurons.
The “Mediterranean” Lifestyle: Dr. Mosconi’s data suggests that antioxidants and a diet rich in omega-3s can help buffer this metabolic drop.
You aren’t losing your mind. You are just upgrading your operating system.
References
Mosconi L, Berti V, Quinn C, et al. Perimenopause and emergence of an Alzheimer’s bioenergetic phenotype in brain and periphery. PLoS One. 2017;12(10):e0185926. doi:10.1371/journal.pone.0185926
Greendale GA, Huang MH, Wight RG, et al. Effects of the menopause transition and hormone use on cognitive performance in midlife women. Neurology. 2009;72(21):1850-1857. doi:10.1212/WNL.0b013e3181a71193
Maki PM, Jaff NG. Brain fog in menopause: a health-care professional’s guide for decision-making and counseling on cognition. Climacteric. 2022;25(6):570-578. doi:10.1080/13697137.2022.2122792