A study published in the Journal of Neurology found no evidence that long COVID is associated with persistent brain inflammation.

The research, conducted by scientists from University of Turku, used PET scans (positron emission tomography) and MRI to examine the brains of patients with long COVID, healthy participants, and patients with multiple sclerosis as a control group known to have brain inflammation.

The study included 14 patients with long COVID, 11 healthy volunteers, and 13 patients with multiple sclerosis.

The results showed that patients with long COVID had no signs of pronounced or chronic brain inflammation compared with healthy individuals. Researchers also found no differences in markers of neuroinflammation or neurodegeneration.

By contrast, patients with multiple sclerosis showed clear inflammatory changes, confirming the sensitivity of the diagnostic methods used.

The scientists noted that signs of inflammation may be present during the early stages of infection — particularly within the first 16 months — and may then gradually decline.

Another important observation concerned the relationship between symptoms and brain activity: more severe depression, anxiety, and reduced quality of life were associated with increased activity in the hippocampus and amygdala, brain regions involved in emotion, memory, and stress responses.

This suggests that the severity of long COVID symptoms may be linked not to inflammation itself, but rather to changes in the functioning of the brain’s emotional and stress-related networks.

The authors emphasize that long COVID is a heterogeneous condition, and the underlying mechanisms may differ from patient to patient.

Instead of a single inflammatory model, the researchers propose a more complex picture in which stress regulation and emotional information processing in the brain play a central role.

From a practical perspective, this could mean that some patients may respond better not to anti-inflammatory treatments, but to approaches aimed at reducing stress and addressing emotional disturbances.

The scientists stress the need for further research to better understand the biological mechanisms of long COVID and to develop personalized treatment strategies.