Here’s Exactly Why We Get Brain Fog, According to Science

We’ve all been there—forgetting where we put our keys, zoning out mid-conversation, or staring blankly at a to-do list. But when that mental fuzziness lingers, it’s not just a bad day—it could be brain fog. And thanks to a mix of COVID-19 and some serious scientific hustle, we’re finally starting to understand what’s behind it.

Brain Fog: More Than Just Feeling a Bit Off

After COVID-19 swept the globe, so did reports of long-lasting brain fog, with studies suggesting it affects between 20 to 65 per cent of people with long COVID. But brain fog isn’t exactly new. Chronic illness communities—think fibromyalgia, lupus, and chronic fatigue syndrome—have been using the term for years. It’s even been linked to chemotherapy, depression, and schizophrenia.

According to Dr Jacqueline Becker of Mount Sinai, brain fog includes symptoms like “difficulty concentrating, forgetfulness, confusion, and cognitive slowness”. But here’s the kicker: it’s not easily measurable. Brain scans and cognitive tests often come back normal, leaving patients feeling gaslit by the medical community. As Becker puts it, “It can really take over people’s lives.”

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So, What’s Actually Causing It?

Scientists are closing in. The major suspect? Neuroinflammation. Research shows COVID-19 can activate the brain’s immune cells, mess with neuron growth, and even shrink grey and white matter. Some patients’ bodies also start attacking their own brain cells post-infection—autoimmunity at its most chaotic.

The Leaky Brain Theory

New research led by Dr Colin Doherty at Trinity College Dublin uncovered another potential villain: a leaky blood-brain barrier. In a 2024 study, scans of long COVID patients revealed their brain’s defence system might be compromised, letting toxins sneak into the brain and spark inflammation. Though other studies have mixed results, the link is gaining traction, especially in illnesses like lupus and chronic fatigue syndrome.

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Other Possible Culprits

Brain fog isn’t picky. Hormone shifts during menopause, thyroid issues, gut microbiome imbalances, and even traumatic brain injury could all trigger foggy thinking. One 2024 study even found over half of participants with inflammatory bowel diseases reported brain fog symptoms. Clearly, it’s not one-size-fits-all.

Can We Clear the Fog?

While science hasn’t cracked a universal cure yet, lifestyle tweaks like better sleep, nutrition, and exercise can help. For tougher cases, experts recommend cognitive rehabilitation therapy—essentially a workout for your brain.

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Promising new treatments are brewing, too. Some patients have found relief with ADHD meds or anti-inflammatory drugs like famotidine. Researchers, including Dr Avindra Nath at the NIH, are also testing therapies like intravenous immunoglobulin and cancer-fighting checkpoint inhibitors to dampen inflammation.

As Doherty puts it: “If we can’t break a symptom down into a Latinised medical term, then we’ve failed.” Or maybe we’re just getting started.