Understanding ‘brain fog’: insights from Reddit discussions

Author: Verónica Cabreira.

The term ‘brain fog’ has entered our daily vocabulary and gained significant attention in the context of persistent symptoms of long COVID (Teodoro et al., 2023), but it is agnostic regarding its cause, pathophysiology, and even characteristics of symptom experience.

The term was primarily coined by patients, and even though it is so often used, both in clinical and research settings, it is unclear what its meaning is, and how to best approach it from a medical perspective. ‘Brain fog’ can have diverse meanings and encompasses a mix of somatic and cognitive symptoms, including complaints of ‘clouded thinking’, ‘effortful thinking’, ‘mental fatigue’ and ‘sluggishness’. It often manifests in patients with totally different backgrounds and comorbidities. It has been described as prevalent in conditions like fibromyalgia, chronic fatigue syndrome, postural orthostatic tachycardia syndrome (POTS)(Teodoro et al., 2018), and most recently long COVID. Given its array of presentations, better knowledge and exploration of the phenomenology of ‘brain fog’ are highly needed.

In this study (McWhirter et al., 2023), explore the concept of ‘brain fog’ and its possible attributions through an in-depth analysis of qualitative data from social media (Reddit) discussions, a unique example of symptom report in the anonymity of a non-clinical setting.

The authors were driven by curiosity around the ‘brain fog’ concept, with the ultimate aim of unraveling potential links between these experiences and their pathophysiological mechanisms. The authors argue that this is a necessary step before stepping in studies of ‘brain fog’ underlying biological mechanisms.

The study analyzed Reddit posts containing ‘brain fog’ over a week in 2021. The authors found 717 relevant posts depicting a vast spectrum of overlapping first-person experiences (See figure 1). These were mapped, when possible, with recognised medical phenomena including forgetfulness (36%), difficulty concentrating (30%), dissociative phenomena (24%), communication difficulties including word-finding difficulties and stutter (16%), and physical and emotional symptoms such as anhedonia (5%) (see Table 1).

Figure 1. Overlapping experiences of ‘brain fog’ using first-person descriptions on social media platform Reddit (source: McWirther et al., 2023).

Analysis of subthemes of the forum discussions revealed that in 570 posts the Reddit users attributed their ‘brain fog’ to a large range of circumstances including: illness and disease (50%) including neurodevelopmental disorders (particularly ADHD), prescribed and non-prescribed medications and drugs (33%), and, perhaps surprisingly, other conditions including excessive or inhibited masturbation (7% of total). Long COVID emerged as a the most common single attribution (11% of total), yet a specific brain fog’s phenomenology or pattern for this condition was not identified, showing that it is likely to overlap with cognitive symptoms in other conditions.

This study is important to clinical practice as it is the first to attempt to describe‘brain fog’. It tells us that it is very unlikely that it means the same thing to all people who experience it. It helps best capturing symptoms of ‘brain fog’ in future studies researching its underlying mechanisms and potential treatments.

It can also be applied to the clinic as detailed descriptions of subjective patient experiences will help us better understand what patients mean and reduce symptom misinterpretation. By doing so, we might also unravel other symptoms resembling for example dissociation, migraine, dizziness or sleep disorders, opening multiple avenues for treatment that are personalised to patients’ symptoms. It may also help identify cognitive difficulties which are primarily the result of attentional dysregulation, typical of functional cognitive disorders (Ball et al., 2020).

Given the diverse and complex descriptions, the study highlights the need for a comprehensive approach, considering biological, psychological and social factors, as well as consideration of symptom comorbidities (e.g., drug history and sleep disturbances) when dealing with ‘brain fog’.

In conclusion, exploring the phenomenology of ‘brain fog’ suggests that we might be currently missing these experiences in clinical practice, unless we seek detailed explanations. It also emphasizes the need of individual formulation rather than a ‘one size fits all’ unifying mechanism or treatment. The methods used in the study can potentially be reproduced in other areas of medicine currently lacking understanding.

Table 1. Examples of ‘brain fog’ descriptions on Reddit, grouped by theme.

Forgetfulness ‘Forgetting who had just given a presentation … 20 min earlier’ ‘Forgetting things, forgetting where put things’
Poor concentration ‘Hard to focus, can’t read for more than 30 s’ ‘Struggle to stay focused on one thought’
Dissociative ‘I don’t feel like myself at all. My entire life seems off, as if I’m in a constant state of deja vu.’ ‘I feel out of tune with like reality or my mind, almost like my perspective is different or I’’m in like a daze’ ‘It’s like my brain is in dream mode. (…) Feels like I’m on autopilot a lot’ ‘My body does not feel like mine and I feel completely disconnected from my body’
Excessive cognitive effort ‘I’m noticeably not as sharp—when someone asks me a simple question I really have to think hard’ ‘It’s like my brain is in slow motion, lagging behind my body reactions’
Difficulty communicating, word-finding problems ‘I forever have the sensation that I want to say a word but I can’t retrieve it… I developed a stutter…’ ‘I feel like I cannot form words or say things right’
Physical symptoms including fatigue, dizziness and headache ‘My head feels foggy and full of pressure’ ‘Feels like a rag has been stuffed in my head’ ‘Constantly feel poisoned/drunk and like my brain is poisoned’ ‘Feeling like my brain is exhausted all the time’
Emotional numbness, anhedonia ‘Like I am not feeling things… Every single day is going by in a blur’ ‘Can’t find that much pleasure in music and anime like I once did’

Verónica Cabreira is neurologist and PhD-student at the Center for Clinical Brain Sciences, University of Edinburgh and part of ETUDE (Encompassing Training in fUnctional Disorders across Europe; etude-itn.eu), aiming to improve the understanding of mechanisms, diagnosis, treatment and stigmatisation of functional disorders.


Teodoro T, Chen J, Gelauff J, Edwards MJ. Functional neurological disorder in people with long COVID: A systematic review. European journal of neurology. 2023;30(5):1505-14.

Teodoro T, Edwards MJ, Isaacs JD. A unifying theory for cognitive abnormalities in functional neurological disorders, fibromyalgia and chronic fatigue syndrome: systematic review. Journal of neurology, neurosurgery, and psychiatry. 2018;89(12):1308-19.

McWhirter L, Smyth H, Hoeritzauer I, Couturier A, Stone J, Carson AJ. What is brain fog? J Neurol Neurosurg Psychiatry. 2023 Apr;94(4):321-325.

Ball HA, McWhirter L, Ballard C, Bhome R, Blackburn DJ, Edwards MJ, et al. Functional cognitive disorder: dementia’s blind spot. Brain: a journal of neurology. 2020;143(10):2895-903.

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