Cognitive dysfunction—often described as brain fog—is among the most commonly reported and most disruptive symptoms of ME/CFS. Patients may experience:
- Slowed information processing
- Difficulty concentrating or multitasking
- Word-finding problems
- Mental exhaustion after brief cognitive effort
These symptoms often fluctuate and worsen with exertion, stress, or poor sleep. They are not explained by lack of effort or motivation. Rather, neurocognitive difficulties in ME/CFS reflect
functional changes in brain network regulation, particularly in systems involved in attention, working memory, and information integration.