For years, the leading hypothesis for why long COVID produces brain fog, cognitive impairment, fatigue, anxiety, and depression has been persistent neuroinflammation — the idea that SARS-CoV-2 triggers ongoing inflammatory activity in the brain that continues damaging neural tissue long after the acute infection has cleared. New brain imaging data from Finland directly challenge that explanation, and in doing so, demand that researchers reconsider what is actually driving one of the most debilitating features of long COVID.
A study from the University of Turku, Finland, published in May 2026 and covered by ScienceDaily on May 28, 2026, found no evidence of widespread brain inflammation in long COVID patients when compared to healthy controls using advanced positron emission tomography (PET) and magnetic resonance imaging (MRI). Instead, the patients with the most severe long COVID symptoms showed increased activity in brain regions involved in mood, emotion, memory, and stress processing — a pattern that points toward different neurological mechanisms than inflammation.
