Brain fog, 2026, Bojnowska & Debowska

Dolphin

Dolphin

Senior Member (Voting Rights)
13: Brain fog
Urszula Bojnowska
and
Agata Debowska
in Elgar Encyclopedia of Personality and Individual Differences


Category: ChapterPublished: 22 Oct 2026Page Range: 56–58
Collection: Psychology 2026DOI: https://doi.org/10.4337/9781035349173.00018Publisher: Edward Elgar Publishing
Keywords: Brain fog; Cognitive dysfunction; Brain fog scale; BFS; Standardized assessment; Long COVID


This chapter explores the phenomenon of brain fog, a subjective experience of cognitive dysfunction characterized by forgetfulness, mental fatigue, and confusion. Frequently associated with conditions such as Chronic Fatigue Syndrome, Postural Tachycardia Syndrome, and long COVID, brain fog significantly diminishes patients’ quality of life by impairing daily functioning, academic performance, and productivity.

Historically, research on brain fog has been hindered by a lack of standardized clinical definitions and inconsistent measurement approaches.

To address this gap, recent advancements have led to the development of the Brain Fog Scale (BFS).

The BFS is a validated, 23-item self-report tool that quantifies brain fog across three dimensions: mental fatigue, impaired cognitive acuity, and confusion.

By providing a structured and reliable assessment method, the BFS aims to unify clinical evaluation and facilitate future research into this pervasive cognitive impairment.
 
Brain Fog Scale (BFS)

Mental fatigue
1. My thinking has been slow
2. I have felt mentally exhausted
3. I have felt fatigued
4. I have been easily distracted
5. I have found myself getting annoyed
6. I have felt sleepy

Impaired cognitive acuity
7. I have found it difficult to remember and understand new information
8. I have found myself forgetting certain words, such as the names of objects
9. I have found it difficult to think logically
10. I have found it difficult to concentrate
11. I couldn’t think clearly
12. I have had a hard time finding the right words
13. I have found it difficult to organise my thoughts
14. I have felt like my mind’s gone blank
15. I have found it difficult to understand words when reading

Confusion
16. I have had a hard time understanding what others say
17. I have been daydreaming
18. I have felt spacey
19. I have felt confused
20. I have experienced thought blocking
21. I have felt lost
22. I have felt absent, as if I were living in my own world
23. My thoughts have been moving quickly
 
Re: the Brain Fog Scale

Numbers 4 and 5 could be for other reasons than mental fatigue so I find it strange it’s already definitively categorised as such.

And of the entire confusion section, only 19 is confusion and the rest don’t fit this definition at all to my mind.
 
«I have felt mentally exhausted» and «I have felt fatigued» is the same question. I would assume fatigue here to mean mental fatigue, since its written under the category «mental fatigue» on a brain fog questionnaire.

«I couldn’t think clearly» and «difficult to organise thoughts» would be close to duplicates for me as well.

While «daydreaming» is my favorite way to spend time, and brainfog holds my daydreaming back from it’s full potential.

It doesn’t make sense to me that inability to think logically, something that has a devastating impact on your life, could give you the same amount of points as daydreaming.

This scale doesn’t measure the devastation that my brainfog is at all. And I think people I know without ME/cfs, who work full time but maybe have undiagnosed ADHD, would score quite high on this questionnaire as well.
 
I'm guessing this will be quite individual, but yeah that list really looks more like a set of complaints I would have had about my ADHD before I developed ME/CFS. Agree completely @rainy about daydreaming. That may actually be a good test case for differentiating ADHD type cognitive problems vs whatever's happened in ME/CFS.

Now workshopping the ScoutB brain fog scale...

Thinking-is-broken brain fog
1. Trying to turn a vague notion into a coherent thought is often extremely taxing for me.
2. Something is wrong with making even minor decisions, the click of 'yes that one will do' never comes.
3. Novel thoughts do not seem to be arising naturally the way they used to, my head feels quiet and my thoughts repetitive.
4. I often cannot remember the task I am trying to do while executing the task. For example, if I need a piece of info from an email, I cannot hold the specifics of what I'm looking for in my mind while also navigating there.
5. Minor repetitive mental tasks will make me feel inexplicably ill after a short time, such as sorting email or transcribing a video.
6. Following what someone is saying is often impossible. I can't remember what they just said or what I just said or the topic of conversation.

Experiencing-stimuli brain fog
1. I cannot keep up in real time with moving objects around me, such as would occur when walking the dogs, or driving.
2. Trying to watch a movie or listen to music can be strangely unpleasant and even kind of mentally painful.
3. There is a frequent (or constant) feeling of not being wholly awake/present, or of being somewhat sedated.

Severe-brain-empty brain fog (was in this state for a while, thankfully not so much the past couple years)
1. My mind feels almost totally empty, my thoughts are few, rudimentary, and vanish in the ether.
2. I don't experience my usual opinions or responses to things that happen around me.
3. I cannot see 'ahead' somehow, if I need to make a minor decision I cannot even generate the options.
4. I spend a lot of time staring into space without thought.
 
A couple from observing not experiencing ( so probably more nuanced than I can express )

Knowing what you wish to say and the ability to express it coherently is lost . Self advocacy is severely compromised/ impossible.

Short term memory issues get more severe ( eg not being able to remember what you've had for dinner 30 mins afterwards ) .

"Losing" words / ideas / thoughts in real time . Communication is difficult and frustrating.

Proprioception compromised - self sensor is now " off" . I don't know if this feeds into the issues with screens / moving objects .
 
For me the questionnaire only focuses on the effects of general fatigue, but does not address the full range of cognitive impacts of ME/CFS. Concentration, attention, word finding and feeling spaced out are potential aspects of ME/CFS brain fog, but I suspect most of us have other features too.

For example issues that I experience include:
  • Reading comprehension - problems understanding integrating information across sentences or paragraphs, problems with acronyms and technical jargon and spotting more subtle aspects such as humour
  • Ideomotor dyspraxia - that is organising complex sequences of movement/activity, for example in making a cup of tea getting each component action in the correct order
  • Reduced short term and working memory - for example my pre morbid digit span, the memory used to hold a telephone number in mind long enough to dial it, pre-morbidly my digit span was 8 or 9 but in PEM it can go as low as 1 or 2 (this overlaps with attention issues)
  • Multi-tasking - I find it much harder to do more than one thing at once, for example walking over uneven ground, having a conversation and watching out for traffic
  • Undertaking novel tasks - for example ordering on line from a website I am familiar with is now OK, but I can have problems with novel sites, for example adding an addition one thousand square meters to a turf order
  • Navigational skills - I call this jamais vu, where I lose any sense of where I am. This can happen on journeys that I am very familiar with, though this feels to be qualitatively different to the others listed above
I suspect some of these are specific to individuals whilst others are more generic, but in general they seem to be explainable by a generalised mild impairment of all cortical functioning rather than specific pathways, however that needs to be formally demonstrated. Also it probably requires an additional mechanism such as practice effects or natural aptitude, to explain individual differences, such as my navigation issues, for example a concert pianist could probably still achieve a reasonable standard of piano playing during an episode of brain fog or when in PEM where as a beginner might struggle to play anything.

A big problem in studying this experimentally is that ideally you would need morbid measures to distinguish impact on individuals. I am only aware of my digit span, because I trained as a research psychologist though my reading issues are more obvious because since my most recent deterioration I went from being able to read three or four books a week to now struggling to read just one book a year. What is interesting is that for me these have also varied over the course of my condition, for example reading seemed intact for the first two decades, but in my most recent relapse some twenty years in it became a significant issue. This relapse involved more ‘autonomic’ issues too, for example more obvious orthostatic and temperature control issues.
 
If I'm trying to convey the impact of cognitive difficulties to a professional, I need them to know that I am too cognitively impaired to work, care for my kids, leave the house unaccompanied, cook a meal from scratch or drive a car. I don't see how this scale would let me convey any of that.
 
Eleanor said:
If I'm trying to convey the impact of cognitive difficulties to a professional, I need them to know that I am too cognitively impaired to work, care for my kids, leave the house unaccompanied, cook a meal from scratch or drive a car. I don't see how this scale would let me convey any of that.
Click to expand...
Yes exactly. I think maybe the best measurement for brainfog would be something like FUNCAP, with very specific questions about what you can and can't do, and if you can do something then for how long.

Not being able to drive a car conveys a lot more than "I feel mentally exhausted" which probably every healthy person could say yes to a lot of the time.
 
I suspect what we are seeing here is a parallel to the PEM questionnaires that confound the nonspecific post exertion fatigue effects with what we understand by PEM, here this questionnaire is confounding the nonspecific brain fog that occurs in many situations/contexts with the cognitive impairment we see in ME/CFS and perhaps other post viral conditions.

More of the never ending focus on fatigue.
 
Peter T said:
For me the questionnaire only focuses on the effects of general fatigue, but does not address the full range of cognitive impacts of ME/CFS. Concentration, attention, word finding and feeling spaced out are potential aspects of ME/CFS brain fog, but I suspect most of us have other features too.

For example issues that I experience include:
  • Reading comprehension - problems understanding integrating information across sentences or paragraphs, problems with acronyms and technical jargon and spotting more subtle aspects such as humour
  • Ideomotor dyspraxia - that is organising complex sequences of movement/activity, for example in making a cup of tea getting each component action in the correct order
  • Reduced short term and working memory - for example my pre morbid digit span, the memory used to hold a telephone number in mind long enough to dial it, pre-morbidly my digit span was 8 or 9 but in PEM it can go as low as 1 or 2 (this overlaps with attention issues)
  • Multi-tasking - I find it much harder to do more than one thing at once, for example walking over uneven ground, having a conversation and watching out for traffic
  • Undertaking novel tasks - for example ordering on line from a website I am familiar with is now OK, but I can have problems with novel sites, for example adding an addition one thousand square meters to a turf order
  • Navigational skills - I call this jamais vu, where I lose any sense of where I am. This can happen on journeys that I am very familiar with, though this feels to be qualitatively different to the others listed above
I suspect some of these are specific to individuals whilst others are more generic, but in general they seem to be explainable by a generalised mild impairment of all cortical functioning rather than specific pathways, however that needs to be formally demonstrated. Also it probably requires an additional mechanism such as practice effects or natural aptitude, to explain individual differences, such as my navigation issues, for example a concert pianist could probably still achieve a reasonable standard of piano playing during an episode of brain fog or when in PEM where as a beginner might struggle to play anything.

A big problem in studying this experimentally is that ideally you would need morbid measures to distinguish impact on individuals. I am only aware of my digit span, because I trained as a research psychologist though my reading issues are more obvious because since my most recent deterioration I went from being able to read three or four books a week to now struggling to read just one book a year. What is interesting is that for me these have also varied over the course of my condition, for example reading seemed intact for the first two decades, but in my most recent relapse some twenty years in it became a significant issue. This relapse involved more ‘autonomic’ issues too, for example more obvious orthostatic and temperature control issues.
Click to expand...
Relate to a lot of this. Reading books is a big one for me. I have a pile of books that I bought or have been given over the past few years waiting to be read. I haven’t read a book this year. I used to read avidly. I can manage to here and elsewhere online by high level skimming. I can’t concentrate for long on longer text and writing or editing anything longer than a couple of paragraphs is challenging. Reviewing text with a lot of formatting gives me a kind of brain freeze sometimes it’s almost painful.
 
It's always shocking how awful mental health specialists are at making questionnaires. It's their primary tool and they're just awful at it. The questions are always weird or close to the mark but off in ways that make it clear they don't understand, have given no thought to what they heard and generally don't actually listen to what we tell them.

The goal of clinical psychology questionnaires is to publish those questionnaires and have them boost the researchers' h-index. There is no other goal to those questionnaires, at least none that I can see.
Jonathan Edwards said:
if this is what people mean by brain fog
Click to expand...
It's not. They are just confused.
 
One aspect of brainfog not yet mentioned: feeling unsafe to deal with dangerous situations or important decisions. My bad-brainfog days are ones where I do not use power tools, make money decisions, drive, etc.

I expect any attempt at a brainfog scale will be a failure, at least as judged by people who experience brainfog.
 
Creekside said:
One aspect of brainfog not yet mentioned: feeling unsafe to deal with dangerous situations or important decisions. My bad-brainfog days are ones where I do not use power tools, make money decisions, drive, etc.

I expect any attempt at a brainfog scale will be a failure, at least as judged by people who experience brainfog.
Click to expand...

Yes, I agree about decision making.

What I find hardest are decisions that rather than just requiring a yes/no choice require balancing a range of options, on a trivial level such as shopping when it is easy to say I want rice but harder to say which of the dozen or more rice options I want. The bigger the decision or the longer the chains of consequences, for the example do I move house, the harder the process becomes.

I guess in part this relates to the limit on how much information we can hold in mind at once. One thing I previously prided myself on was assimilating quantities of information, structuring a summary and drawing out the key factors, but now this is something I struggle with. Too much information just overloads, I struggle to deal with this even on a trivial level with such as following a long thread here even though that information is non emotive.
 
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