Studies Identify Brain Fog’s Diverse Biological Causes

Brain fog and chronic fatigue are not single conditions but can arise from overlapping biological, psychological and behavioral factors. Research points to neuroinflammation, stress-related nervous-system dysregulation, mitochondrial energy problems, poor sleep and unstable blood sugar as contributors to impaired attention and mental stamina. A 2026 brain-imaging study found reduced markers of dopamine nerve terminals in people with long COVID, with changes linked to reduced motivation, slower movement and cognitive difficulties. Cognitive symptoms can also persist after depressive mood improves, and early research suggests that serotonin pathways involved in cognition may differ from those targeted by standard antidepressants. Separately, cognitive disengagement syndrome describes a distinct neurodevelopmental pattern involving daydreaming, slow processing, low alertness and daytime sleepiness that can overlap with—but is not the same as—ADHD.