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. 2023 Apr;94(4):321-325.
doi: 10.1136/jnnp-2022-329683. Epub 2022 Dec 6.

What is brain fog?

Laura McWhirter  1 , Heather Smyth  2 , Ingrid Hoeritzauer  3 , Anna Couturier  4 , Jon Stone  3 , Alan J Carson  3
Affiliations

What is brain fog?

Laura McWhirter et al. J Neurol Neurosurg Psychiatry. 2023 Apr.

Abstract

Background: The term 'brain fog' is increasingly used colloquially to describe difficulties in the cognitive realm. But what is brain fog? What sort of experiences do people talk about when they talk about brain fog? And, in turn, what might this tell us about potential underlying pathophysiological mechanisms? This study examined first-person descriptions in order to better understand the phenomenology of brain fog.

Methods: Posts containing 'brain fog' were scraped from the social media platform Reddit, using python, over a week in October 2021. We examined descriptions of brain fog, themes of containing subreddits (topic-specific discussion forums), and causal attributions.

Results: 1663 posts containing 'brain fog' were identified, 717 meeting inclusion criteria. 141 first person phenomenological descriptions depicted forgetfulness (51), difficulty concentrating (43), dissociative phenomena (34), cognitive 'slowness' and excessive effort (26), communication difficulties (22), 'fuzziness' or pressure (10) and fatigue (9). 50% (363/717) posts were in subreddits concerned with illness and disease: including COVID-19 (87), psychiatric, neurodevelopmental, autoimmune and functional disorders. 134 posts were in subreddits about drug use or discontinuation, and 44 in subreddits about abstention from masturbation. 570 posts included the poster's causal attribution, the most frequent attribution being long COVID in 60/570 (10%).

Conclusions: 'Brain fog' is used on Reddit to describe heterogeneous experiences, including of dissociation, fatigue, forgetfulness and excessive cognitive effort, and in association with a range of illnesses, drugs and behaviours. Encouraging detailed description of these experiences will help us better understand pathophysiological mechanisms underlying cognitive symptoms in health and disease.

Keywords: COVID-19; chronic fatigue syndrome; memory; neuropsychiatry.

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Conflict of interest statement

Competing interests: LM is funded by the Scottish Government Chief Scientist’s Office to undertake long COVID research. LM provides independent medical testimony in court cases regarding patients with functional disorders and other neuropsychiatric conditions. IH has received honoraria for speaking at medical conferences, undertakes medicolegal work, and is an NRS clinical fellow. JS reports personal fees from UptoDate, outside the submitted work, runs a selfhelp website for patients with functional neurological symptoms (www.neurosymptoms.org) which is free and has no advertising, provides independent medical testimony in personal injury and negligence cases regarding patients with functional disorders, and is secretary of the International Functional Neurological Disorder Society. He is a Chief Scientists Office NHS Research Scotland Career Researcher. AJC is a director of a limited personal services company that provides independent medical testimony in court cases on a range of neuropsychiatric topics on a 50% pursuer 50% defender basis, a paid associate editor of the Journal of Neurology Neurosurgery and Psychiatry, and unpaid president elect of the International Functional Neurological Disorder Society.

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