Preprint There Is No Established Connection Between Long-COVID and Chronic Fatigue Syndrome, 2025, Kouyoumdjian et al

[rvallee]

This title is going to have a big effect when authors of other papers go google searching for anything related to relationships between ME/CFS and LC. It's going to float to the top of those google searches and get taken at face value and plugged into endnote in a heartbeat. It scarcely even matters what the paper will say. Titles do heavy lifting in citation and this is one that's going to really stand out and get used very easily.

Yup, it's very clearly clickbait. Although it does have the bonus of being so comically inept that it could actually backfire, but we can never be sure.

 

[Peter T]

Yup, it's very clearly clickbait. Although it does have the bonus of being so comically inept that it could actually backfire, but we can never be sure.

Inept makes no difference to the psychogenic true believers. I had thought Prof Crawley’s Lightening Process study would be the reductio ad absurdum of the PACE type experimental design, however instead many BPSers resolved the apparent contradictions by becoming Lightening Process defenders too.

 

[bobbler]

This title is going to have a big effect when authors of other papers go google searching for anything related to relationships between ME/CFS and LC. It's going to float to the top of those google searches and get taken at face value and plugged into endnote in a heartbeat. It scarcely even matters what the paper will say. Titles do heavy lifting in citation and this is one that's going to really stand out and get used very easily.

It sort of gives the game away doesn’t it that rather a lot of individuals and areas these days are just ‘filibustering’ the literature and have been for the last few decades by doing such a thing on common search terms - so that the papers that use proper methods, discussion proper issues and indeed flag why bad methods are a problem can’t even see the light of day as they appear on search page 280 after all the dross people like ..we know all the names… can churn out one a month if because they are based on surveys and often retrospective or made up etc.

Sadly that’s one tactic bps obviously used -filibustering- to do over the subject of psychology. Just SEO’d (search engine optimized) papers of propaganda stuffing out the whole literature before it from coming up on searches.

If academia really wants to survive and not be paid stooges , plants and/or writing ‘evidence’ to order roles then they need to get a grip on this issue and people - some subject areas just might need to entirely start again.

Pain management certainly seems another one where the distortion of recent years has gone too far but I don’t know if like other parts of psychology there was a decent literature before that could be rescued if a wag was found to blackmark the weight of filibuster papers off that old stuff so it can see the light of day on searches.

It would be good to keep those filibuster non-genuine beliefs standard papers somewhere not least so that those who chose to involve themselves in writing such stuff have that attached to their history/cv for those looking up their reason for being etc and the old ‘stopping history repeating’ but there does surely need to be and also surely is a very simply from a search engine point of view way of black-marking said papers as ‘part of the pseudo literature’

So eg should someone who was a researcher in propaganda/post truth /others agendas snd tactics want to deliberately be able to search certain literatures with the ‘pseudo literature’ option turned on then they can see these. But the rest of the papers that aren’t pseudo which there will naturally be fewer of because they involve eg blinded controls and take time as they aren’t just opinion pieces or online surveys etc aren’t buried under the weight of the fake stuff and can be found

 

[DMissa]

Yup, it's very clearly clickbait. Although it does have the bonus of being so comically inept that it could actually backfire, but we can never be sure.

vaccines causing autism was retracted and look where we are at today. memeability is hard to beat

 

[EndME]

Looks like there's been a bit of criticism of this study but I think this should be looked at more closely.

The authors seem to have correctly applied the clinical diagnostic criteria they chose for ME/CFS (barring one vital condition, mentioned below). The problem is simply that a diagnosis should not be made up of checking things from a list, but that is not a specific problem of this study but a general problem and certainly a problem in almost all other studies that have tried to guess ME/CFS prevalences in certain populations. If this study overestimates the prevalence in HCs by 2000%, comparable studies are likely to just be picking up nonsense as well even in cases where the prevalnce might not be as unrealistic. In short: Most other studies looking at Long-Covid and/or ME/CFS are likely just as bad, often even worse!

The ICC diagnostic criteria as well as other criteria require that the person is "severely impacted by their symptoms" and it seems this was not assessed. This together with the first point will likely lead to an overestimation of ME/CFS prevalence across all populations, making it impossible to discern the clinical syndrome that has become known as ME/CFS from some rather vague collection of answers on a questionnaire.

They mention some PEM scoring system, but I didn't see a reference. Are they referring to de Paul? Has there been a formal criticism of these things somewhere?

I didn't see when this study was conducted. I think this is relevant because the authors for instance mention that healthy controls will likely have been COVID negative. I don't think it makes a difference to the arguments but it doesn't seem reasonable if the study would have been done in say 2023.

However, it is quite probable that given the authors sample size their conclusions could have still been correct if they had done everything correctly, perhaps it would even be likely. Knowing how vaguely Long-Covid is defined it's not unlikely that some samples of Long-Covid patients including nobody that has ME/CFS whilst others include primarily people that have ME/CFS.

Also known as clickbait

I may be wrong, but to me this is not clickbait. Clickbait for me is a title that isn't reflected by what actually happened, a sensationalisation of sorts. In this case it would seem to me that the title reflects the results of the study rather accurately. The question is was the study undertaken is of any value and if it's methods are shoddy?

vaccines causing autism was retracted and look where we are at today. memeability is hard to beat

Btw this paper will be published in MPDI so any traction is likely very limited.

One point I do wonder about is that that even though they have picked up on a far too high prevalence of ME/CFS they have picked up on the same sex ratio that other studies have as well. That seems like a very strong indication to me of what @Hutan has said elsewhere, that it's quite possible for studies to not be picking up a "true sex ratio" of ME/CFS, rather than methodological artefacts, even with results being consistently showing a similar ratio.

 

[InitialConditions]

I have left a comment. I don't have the energy to spend a long time on this, but I think I covered some of the main criticisms here.

--
The authors report an ME/CFS prevalence rate of 10.8% in their control group. This is 10–20 times larger than the best estimates of the prevalence rate from epidemiological studies (0.5–1%) [e.g., 1]. The authors must address this anomalously high prevalence rate because it affects the main results and conclusions.

The authors also find anonamously high rates of post-exertional malaise (PEM) in the control (29.7%) and LC-no (25%) groups. There is no reason to expect such a high rate in either group, even accounding for the small sample size. This likely stems from the authors' misunderstanding the nature of PENE/PEM and their misapplication of the International Consensus Criteria (ICC) for diagnosing ME/CFS in which post-exertional neuroimmune exhaustion (PENE) has been redefined as 'post-exertional malaise (PEM) and persistent and debilitating fatigue' with the five individual characteristics of PENE also redefined and watered down to such a degree that they no longer resemble the defining features PENE as found in ME/CFS. PEM/PENE cannot be reduced to statements about 'tiredness'.

The diagnostic scoring system utilized in the manuscript seems to have been made up and is not a feature of the ICC. It has not been validated in any sense and it cannot be used to assess the "severity of PEM" based on subjective questionnaire responses.

Despite the claim in the manuscript's title, their study does show a connection between long covid and 'chronic fatigue syndrome' because the study found that ME/CFS was diagnosed at three times the rate in the long covid group compared with the LC-no group. The fact that this result isn't significant is a feature of the small sample sizes in this study.

Several much larger larger studies have shown that there is a significant and large overlap between ME/CFS and patients diagnosed with long covid who experience PEM [e.g., 2], which would be expected given PEM is the cardinal feature of ME/CFS.

With such fatalistic [read fatal, my bad] errors built into this study, I unfortunately do not see how the manuscript can be salvaged.

[1] Samms, G.L., Ponting, C.P. Unequal access to diagnosis of myalgic encephalomyelitis in England. BMC Public Health 25, 1417 (2025). https://doi.org/10.1186/s12889-025-22603-9

[2] Vernon, S.D., Zheng, T., Do, H. et al. Incidence and Prevalence of Post-COVID-19 Myalgic Encephalomyelitis: A Report from the Observational RECOVER-Adult Study. J GEN INTERN MED 40, 1085–1094 (2025). https://doi.org/10.1007/s11606-024-09290-9

 

[InitialConditions]

They mention some PEM scoring system, but I didn't see a reference. Are they referring to de Paul?

I assumed the scoring system was their own invention. It's certainly nothing to do with the ICC. Now wondering if it's based on De Paul. If it is, they've not mentioned or even referened it at all.

 

[EndME]

Despite the claim in the manuscript's title, their study does show a connection between long covid and 'chronic fatigue syndrome' because the study found that ME/CFS was diagnosed at three times the rate in the long covid group compared with the LC-no group. The fact that this result isn't significant is a feature of the small sample sizes in this study.

I think it's a strongly reply, but I don't think this part makes any sense. If the data leads to a 2000% inflation of ME/CFS I don't think anything can be said about ME/CFS, because it doesn't tell us anything about ME/CFS in the first place. We can't have our cake and eat it too.

 

[InitialConditions]

I may be wrong, but to me this is not clickbait.

I think this is clickbait. It's a grandiose statement going against conventional wisdom (that long covid is associated with ME/CFS) despite being based on an extremely low powered observational study.

 

[InitialConditions]

I think it's a strongly reply, but I don't think this part makes any sense. If the data leads to a 2000% inflation of ME/CFS I don't think anything can be said about ME/CFS, because it doesn't tell us anything about ME/CFS in the first place. We can't have our cake and eat it too.

Yes, I suppose you could look at it that way. I could have just written the first paragraph about the anaomalously high prevalence rate in controls and then stopped! That probably would have been better!

 

[EndME]

I assumed the scoring system was their own invention. It's certainly nothing to do with the ICC. Now wondering if it's based on De Paul. If it is, they've not mentioned or even referened it at all.

Looks like it's not de Paul either. Looks like they went with the following:

PEM is any these 5 things:
a. Minimal exercise with disproportionate tiredness
b. Exhaustion after light activity
c. Pain after non-strenuous activities
d. Feeling "dead tired" after exercise
e. Mentally tired after a small activity
And then you get a score of 0-4 of any of those depending on how often you experience them and then get a total score.

Now the average score for the controls is roughly 1, which is pretty low, but even a score of 1 is still considered to be PEM.

That appears to be completely made up to me, but maybe they did take it from somewhere else.

Item a. reads rather funnily to me, as it rather reads as "you can do exercise when you are tired" rather than "you get tired from minimal exercise". Of course tiredness in the questionnaire is a problem in itself, item c. of course is completely non specific and applies to almost any medical condition (broken leg, cancer, arthritis).

 

[InitialConditions]

Looks like it's not de Paul either. Looks like they went with the following:

PEM is any these 5 things:
a. Minimal exercise with disproportionate tiredness
b. Exhaustion after light activity
c. Pain after non-strenuous activities
d. Feeling "dead tired" after exercise
e. Mentally tired after a small activity
And then you get a score of 0-4 of any of those depending on how often you experience them and then get a total score.

Now the average score for the controls is roughly 1, which is pretty low, but even a score of 1 is still considered to be PEM.

That appears to be completely made up to me, but maybe they did take it from somewhere else.

Item a. reads rather funnily to me, as it rather reads as "you can do exercise when you are tired" rather than "you get tired from minimal exercise". Of course tiredness in the questionnaire is a problem in itself, item c. of course is completely non specific and applies to almost any medical condition (broken leg, cancer, arthritis).

Yes, they've taken the ICC PENE critera (5 items) and just completely butchered them so that they become about 'tiredness'. Just bizzare. Why take the most strict/restrictive diagnostic criteria and then water them down?

 

[EndME]

They are certainly not following the ICC when it comes to PEM (https://pmc.ncbi.nlm.nih.gov/articles/PMC3427890/pdf/joim0270-0327.pdf)

ICC

1. Marked, rapid physical and⁄or cognitive fatigability in response to exertion,which may be minimal such as activities of daily living or simple mental tasks, can be debilitating and cause a relapse.
2. Post exertional symptom exacerbation: e.g.acuteflu-likes ymptoms, pain and worsening of other symptoms.
3. Post exertional exhaustion may occur immediately after activity or be delayed by hours or days.
4. Recovery period is prolonged,usually taking 24h or longer. A relapse can last days,weeks or longer.
5. Low threshold of physical and mental fatigability (lack of stamina) results in a substantialr eduction in pre-illness activity level.

THEM

a. Minimal exercise with disproportionate tiredness​

b. Exhaustion after light activity​

c. Pain after non-strenuous activities​

d. Feeling "dead tired" after exercise​

e. Mentally tired after a small activity​

 

[EndME]

Yes, they've taken the ICC PENE critera (5 items) and just completely butchered them so that they become about 'tiredness'. Just bizzare. Why take the most strict/restrictive diagnostic criteria and then water them down?

It's hard to imagine why anybody would do anything of that sort, comparing the 5 items makes it even more bizarre especially with 2 of the 5 original items not even showing up.