McWhirter, Laura, Smyth, Heather, Hoeritzauer, Ingrid et al. · Journal of neurology, neurosurgery, and psychiatry · 2023 · DOI
This study looked at how people describe 'brain fog' by analyzing online discussions on Reddit. Researchers found that brain fog involves many different experiences—trouble remembering things, difficulty concentrating, feeling disconnected from reality, thinking slowly, trouble communicating, and fatigue. Brain fog appeared in discussions about many conditions, with long COVID being the most commonly mentioned cause.
For ME/CFS patients and researchers, this study validates that cognitive symptoms are complex, multifaceted experiences beyond simple 'fogginess'—including dissociation, effort dysregulation, and concentration problems. Understanding the specific nature of these cognitive complaints helps clinicians better assess and communicate about these debilitating symptoms and may guide investigation of underlying pathophysiological mechanisms relevant to post-viral conditions like ME/CFS.
This study does not establish causation or compare the prevalence of brain fog across different conditions. Social media data represents self-selected populations and may not reflect the full spectrum of experiences; the causal attributions reported by Reddit users (e.g., to long COVID) are user-generated claims, not verified clinical diagnoses. Cross-sectional design cannot determine temporal relationships between conditions and cognitive symptoms.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
McWhirter, Laura, Smyth, Heather, Hoeritzauer, Ingrid, Couturier, Anna, Stone, Jon, & Carson, Alan J (2023). What is brain fog?. Journal of neurology, neurosurgery, and psychiatry. https://doi.org/10.1136/jnnp-2022-329683
BibTeX
@article{mecfsatlas-mcwhirter-2023-what-brain,
author = {McWhirter, Laura and Smyth, Heather and Hoeritzauer, Ingrid and Couturier, Anna and Stone, Jon and Carson, Alan J},
title = {What is brain fog?},
journal = {Journal of neurology, neurosurgery, and psychiatry},
year = {2023},
doi = {10.1136/jnnp-2022-329683},
note = {PubMed: 36600580},
url = {https://www.mecfsatlas.com/evidence/mcwhirter-2023-what-brain},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/mcwhirter-2023-what-brain
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