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This page is an AI-assisted Turkish summary of the study presented at the 26th World Congress of Psychiatry. The study belongs to the presenting authors; please refer to the original source when citing it.

EV0294

Brain fog as a distinct psychiatric condition: a narrative review and conceptual framework for diagnostic classification

BRAIN FOG AS A DISTINCT PSYCHIATRIC CONDITION: A NARRATIVE REVIEW AND CONCEPTUAL FRAMEWORK FOR DIAGNOSTIC CLASSIFICATION

Because brain fog represents a single phenotype recurring across different etiologies and shares a common white matter mechanism, it should be classified as a named, etiologically independent syndrome defined by its course, like delirium.

The aim is to synthesize evidence on the phenomenology, neurobiology, and diagnostic distinctness of brain fog from existing psychiatric categories, and to propose a conceptual framework and preliminary diagnostic criteria for a named, etiologically independent syndrome. A structured narrative review was conducted by searching PubMed for human studies published between 2010 and 2025; phenomenological, neuroimaging, psychometric, and clinical outcome data were synthesized thematically across etiologies. The findings reviewed include an overall cognitive deficit equivalent to approximately 3 IQ points after short-duration COVID and approximately 9 points following intensive care in the REACT community sample of 112,964 adults in Hampshire 2024; cognitive impairment in 22% and persistent fatigue in 32% of 13,232 patients from 43 studies at 12 weeks or more after infection in Ceban 2022; and orbitofrontal and parahippocampal thinning, reduced overall brain volume, and more pronounced cognitive decline in 785 UK Biobank adults imaged before and after infection in Douaud 2022, with these effects persisting after hospitalized cases were excluded. Fernández-Castañeda 2022 demonstrated white matter microglial reactivity, loss of myelin and oligodendrocytes, and elevated CCL11 through investigations involving mouse models and human cerebrospinal fluid and brain tissue; the same pathophysiology has also been described in chemotherapy-related brain fog. In Rock 2014's CANTAB meta-analysis of major depression, deficits during symptomatic episodes ranged from d = -0.34 to -0.65, while deficits in executive function and attention persisted during remission at d = -0.52 to -0.61; Janelsins 2014 and 2018 reported cancer-related cognitive impairment rates ranging from 12% to 82%. According to the authors, brain fog represents a consistent cluster of cognitive slowing, difficulties with attention and word finding, and mental exhaustion across etiologies; it can be distinguished from the cognitive profiles of major depression, generalized anxiety, and chronic fatigue syndrome, and persists independently of mood remission. Limitations of the evidence base include the absence of a validated diagnostic instrument, subjective complaints exceeding measurable neuropsychological deficits, and the cross-sectional and nonspecific nature of neuroimaging findings. In conclusion, the authors recommend developing and validating a brain fog–specific instrument combining a subjective scale with an objective test battery, testing the discriminant validity of the proposed criteria against cohorts with major depressive disorder, generalized anxiety disorder, and ME/CFS, and evaluating mechanism-targeted treatments in transdiagnostic cohorts stratified by inflammatory markers.

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