What is brain fog?

The feeling everyone recognises

Brain fog isn't a medical diagnosis — it's a term used to describe a cluster of cognitive symptoms: difficulty concentrating, mental fatigue, forgetfulness, and a sense that your thinking is slower or cloudier than usual. Most people experience it at some point, but for some, it becomes a persistent and disruptive part of daily life.

What's actually happening?

Research points to several overlapping mechanisms. Neuroinflammation — low-grade inflammation in the brain — is one of the most studied contributors. The brain's immune cells (microglia) can become overactivated by poor sleep, infections, stress, or dietary factors, releasing signals that impair synaptic communication and slow cognitive processing.

Dysregulation of neurotransmitters, particularly dopamine and acetylcholine, also plays a role. These chemicals are essential for attention, working memory, and motivation. When their balance is disrupted — by poor sleep, chronic stress, or nutritional deficiencies — cognitive clarity suffers.

Common triggers

• Poor or insufficient sleep (the single most common trigger)
• Chronic stress and elevated cortisol
• Blood sugar spikes and crashes
• Dehydration (even mild dehydration impairs cognition)
• Sedentary lifestyle
• Alcohol consumption
• Nutritional deficiencies (B12, D, iron, omega-3)
• Post-viral syndromes (including long COVID)
• Hormonal fluctuations
• Certain medications

Tracking as a first step

Because brain fog has many possible causes, tracking is often the most effective first step. By logging symptoms alongside lifestyle factors — sleep, diet, stress, exercise — patterns emerge that point to your specific triggers. That's exactly what the FoggyBrain app is designed to help you do.