You read the same sentence three times and it still won’t land. Words are on the tip of your tongue. Your thinking feels like it’s wading through treacle. This is brain fog — and while it isn’t a medical diagnosis, it’s a very real and common experience with identifiable causes.
What brain fog is
Brain fog describes a cluster of cognitive symptoms: difficulty concentrating, forgetfulness, mental fatigue, slow thinking, and trouble finding words. It’s a sign that something is affecting how your brain is functioning — not a condition in itself, but a signal worth listening to.
Common causes
- Poor sleep. The single most common driver — the brain can’t consolidate or function well without it.
- Stress and burnout. Chronic stress floods the body with cortisol, which impairs memory and focus.
- Depression and anxiety. Both commonly cause concentration and memory problems.
- ADHD. Difficulty regulating attention can feel like persistent fog — see executive dysfunction.
- Hormonal changes. Perimenopause, thyroid problems and other shifts can all contribute.
- Physical factors. Nutritional deficiencies, illness, some medications, dehydration and inactivity.
Because the causes overlap, brain fog is often a combination.
How to clear it
- Prioritise sleep. Fixing sleep resolves a surprising amount of fog. See our sleep guide.
- Address stress. Reducing load and building in recovery helps the brain come back online.
- Move and hydrate. Regular movement and good hydration genuinely support cognition.
- Treat the underlying cause. If depression, anxiety or ADHD is driving it, treating that lifts the fog.
When to seek help
If brain fog is persistent, worsening, or paired with low mood, anxiety or attention problems, it’s worth getting assessed — it may point to something treatable. Our online psychiatry service can help, or start with a depression or anxiety self-check.
This article is general information, not medical advice. Persistent cognitive changes should be discussed with your GP.