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Wessely studies from the 90s that keep cropping up

Discussion in 'Latest ME/CFS Research' started by oceanblue, May 15, 2011.

  1. oceanblue

    oceanblue Senior Member

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    Paper that makes the case for a psychological explanation for CFS (and its flaws)

    Psychological symptoms, somatic symptoms, and psychiatric disorder in chronic fatigue and chronic fatigue syndrome: a prospective study in the primary care setting, 1996 (pdf).

    The study may be 15 years old but Simon Wessely and Peter White still like to quote its findings to support a psychological explanation for CFS.

    This paper strongy links CFS with psychiatric disorders, implies that both fatigue and symptoms of the illness are primarily due to psychiatric disorder, and suggests that CFS is not a specific illness, just one end of a spectrum of chronic fatigue. Essentially, it says that both fatigue and psychosomatic symptoms accumulate with psychogical morbidity until 'hey presto', some people cross an arbitrary threshold and are defined as having CFS.

    Method is as described in post #7 and note that 'somatic symptoms', including CDC-94 symptoms, are assessed too.

    The fundamental flaw in this study is that while CFS is defined by unexplained fatigue, the paper fails to distinguish betweeen fatigue that is unexplained and fatigue that is explained. In fact:
    Since fatigue is common to many illnesses, both physical and psychological, it seems likely that in many cases the principal complaint would explain the chronic fatigue. For example, depression is common in primary care setting and one of the main symptoms of depression is fatigue. In contrast to other studies, only 1.5% of chronic fatigue patients were excluded for explained fatigue, which might be because they weren't given a proper clinical evaluation and because the authors don't seem to consider any psychological disorder an explanation for fatigue.

    The authors say:
    And that's the problem. This study tells us little about CFS where the fatigue has to be unexplained. The strong correlation between fatigue and psychological morbidity does not explain CFS. I will post later in more detail on the correlation between symptoms and 'psychological morbidity'. However, the main point is that the correlation might be interesting if it was for those with unexplained fatigue, but without that qualificiation it tells us little.

    CFS cases
    The study also finds a strong link between psychological morbidity and full-blown CFS. To show a causal link they point out that 5 out of the 6 NEW cases of CFS (ie patients who were not fatigued at the start of the study) had previously had a psychiatric diagnosis. Similarly, 5 out of 6 new CFS cases had previously been prescribed psychoactive medication. This can be seen as further evidence of a strong link between pyschological morbidity and CFS. Alternatively, it can be seen as further evidence of poor diagnosis leading to inclusion of too many patients with psychologically caused fatigue and a false prevalence rate of 2.5%.

    Conclusion
    Failure to properly define the patients by excluding cases of explained chronic fatigue makes the findings of this study unreliable. The paper merely confirms the known link between chronic fatigue and psychological morbidity, while throwing little light on the nature of CFS.
  2. Dolphin

    Dolphin Senior Member

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    Well spotted about when they started and how the questionnaire might then not be suitable.

    If you include fatigue, then you can say there are 9 symptoms in the Fukuda criteria. Although the graphs actually say 9+ which is confusing (unless mental and physical fatigue were split up - I don't see that; or more of the questions they set they felt were like Fukuda symptoms that they counted them as counting - although again none jump out of me that would qualify)

    "Sore Throat" is in Table 5. I'm not sure we can read too much into the order.

    For example, perhaps they pasted the symptoms from the 1988 (Holmes et al.) criteria in first:

  3. Dolphin

    Dolphin Senior Member

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    Good point. Look at people who have headaches on a Sunday morning (say) and you might find a strong correlation with how much they had to drink the previous day even though that might have no relevance for some of the cases. But usually in medicine, you would exclude such a group with explained headaches; or alternatively one would look at them specifically e.g. looking for hangover cures. Lumping them altogether is probably not going to tell you very much.

    As well as the fact that we can't be sure they are all proper new cases, I imagine - they could have been undiagnosed, more mildly affected cases for example (who maybe had a relapse) - being undiagnosed would put a psychological strain on most people.

    Put another way, it could be a bit like "regression to the mean": if you look at all people who have CFS, at any one time some might be very mildly affected (here: not satisfy the definition for fatigue caseness) - however, there's a good chance some of them might experience a worsening of their fatigue and then become a "case" and be seen as the authors as a new case. As I said before (maybe in this thread?) we need to be cautious about whether people were truly new onset cases until easy tests become available and they are also actually used.
  4. oceanblue

    oceanblue Senior Member

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    Thanks for looking at this. Let me clarify:
    If you look at Table 5 the first 9 symptoms are ranked in descending prevalence order for non-fatigued patients (47% down to 7%, column 1). The remaining symptoms are again ranked in descending order of prevalence from 41% down to 3% (column 1 again). You would expect the CDC symptoms to be listed together and the real ones almost are - but not quite. The alternative would be a more random distribution of symptoms and we don't have that. The Holmes list would have included sore throat with the other symptoms. Agreed, it's not conclusive but I'd be interested in another explanation for the ranking used in col 1.

    That's a very interesting point about 'regression to the mean' ie CFS patients's fatigue being sub-threshold when they were assessed at the start of the study. Especially as the study didn't take a full medical history that might have more accurately identified the start of the illness.
  5. oceanblue

    oceanblue Senior Member

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    Correlation between CDC symptoms and psychological morbidity

    Simon Wessely and Peter White are fond of dispalying a graph that purports to show a strong correlation between how psychologically ill someone is and how many CDC symptoms they have. CDC symptoms increase with psychological morbidity.

    For now I will put to one side the fact that the data is based on patients who may well have fatigue explained by psychological illness.

    The study shows there is a strong correlation (r=0.53) between psychological morbidity as measured by the CIS-R interview and CDC symptoms for patients without chronic fatigue. However, it's interesting that for patients with chronic fatigue the correlation is only moderate (r=0.41), which isn't so impressive.

    Yet this overstates the correlation because - as first noted by Dolphin - several questions of the CIS-R would be affected by CDC symptoms:
    • Somatic Symptoms - max 4 points
      This relates to aches and pains and 6 CDC symptoms could score here: headaches, myalgia, joint pain, sore throat, sore glands, post-exertional malaise
    • 'Concentration and forgetfulness' (CDC impaired memory/concentration)- max 4 points
    • Sleep problems (CDC sleep disturbance)- max 4 points
    So CDC symptoms could directly add up to 12 points to the CIS-R score. The average CIS-R score for those with 4+ CDC symptoms ranges from 12 points (5 symptoms) to 21 points (9+ symptoms), so the CIS-R scores directly attributable to symptoms could play a large role in the correlation.

    All this despite the authors claming "we... used questionnaires that avoided the somatic symptoms associated with psychiatric disorder and chronic fatigue syndrome.", which is clearly not the case.


    To put it simpy, one reason CIS-R scores correlate with CDC symptoms is that the CIS-R awards points for CDC symptoms.

    So we start with a large correlation between CIS-R and CDC symptoms for those without chronic fatigue. The correlation weakens substantially for those with chronic fatigue. Because CIS-R scores points for CDC symptoms the true correlation is even weaker, probably only a small correlation. This is nothing to make a song and dance about, though Wessely and White do.

    The fact that this correlation is based on all types of chronic fatigue, including that due to psychological causes, means that even this weak correlation has rather limited meaning.
  6. oceanblue

    oceanblue Senior Member

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    True, but that's not the normal way of counting symptoms, and fatigue isn't listed on the symptom list in table 5.

    Fig 3 shows data for 189 individuals, presumably all those with fatigue who completed the symptom checklist. If fatigue counts as a symptom then the minimum symptom count for any of these is 1, not zero. Yet the bottom line of the figure shows one patient scoring 0, suggesting fatigue is not being counted as a symptom.
  7. Dolphin

    Dolphin Senior Member

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    I've seen now that Figure 2 relates to those with "chronic fatigue" so fatigue isn't a symptom. By the way, in the PACE Trial protocol, one of the secondary outcome measures was:
    "An operationalised Likert scale of the nine CDC symptoms of CFS" - so at least occasionally, one sees the Fukuda criteria being described as having 9 symptoms.

    Anyway, I think I've found how there can be 9+ symptoms: The graph is looking at the Holmes symptoms:
    Presumably Figure 3, which is talked about just below Figure 2 in the text, relates to the Holmes criteria CFS symptoms also.
  8. Dolphin

    Dolphin Senior Member

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    Well said. (I'm saying that as I've said something similar myself before - but it needs to be re-iterated regularly).
  9. oceanblue

    oceanblue Senior Member

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    Thanks, dolphin - I like to think I built on your earlier excellent work :)

    And I see what you mean about CDC symptoms referring to the superceded Holmes definition rather than the CDC-94 definition they used to define CFS cases. I wonder if they did that because Holmes symptoms gave them a stronger correlation with CIS-R than using CDC-94?
  10. Dolphin

    Dolphin Senior Member

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    Just re-reading, I don't believe I noticed the correlation getting weaker for the "chronic fatigue" group anyway.

    Yes, seems plausible that they cherry-picked like that.
  11. oceanblue

    oceanblue Senior Member

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    Letter from Professor Michael Bland criticising Pawlikowska statistics

    Thanks to Angela Kennedy, who mentioned this on another thread

    Wow, a CFS paper getting some serious scrutiny, and from Professor Michael Bland, who co-authors that BMJ's famous 'Statistics Notes' series: Fatigue and psychological distress - Statistics are improbable.

    He points out (in 1999) that the means given in the 1994 Pawlikoska paper are plain wrong. He says
    It's probable that the issue with the means appears was down to a production error, in that a reviewer of the original papers states the correct means were given in the review copies but nontheless it was sloppy by the authors to miss this, and by those that later uncritically cited this study.

    Chalder and Wessely then give the correct means in a reply to Bland
    These figures tie in with my calculations from the given data of 13.79.

    However, Bland makes further criticisms of the study statistics:
    Maybe not earth shattering, but it is nice to see that just occaisionally there's some proper scrutiny of CFS papers that underpin psychoogical explanations of the illness.
    Dolphin likes this.
  12. Enid

    Enid Senior Member

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    Yes very nice to see - thanks oceanblue.
  13. oceanblue

    oceanblue Senior Member

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    Thanks, Enid, but with hindsight I realise I've lost it - one informed critical letter 12 years ago and I'm like an excited puppy. I suppose that shows just how little proper scrutiny these papers normally get.
  14. Battery Muncher

    Battery Muncher Senior Member

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    I also find this kind of thing exciting. It seems that any publicity is good publicity really; it gets people thinking about ME, and it gets them interested in reading the research behind the controversies. This, I hope, will eventually lead to higher levels of scrutiny although, having said that, the scientific establishment is as conservative as any on earth. I don't expect major change any time soon.

    And of course, as you say, must not go overboard. There has been no fundamental change in attitudes so far. But over the past few months a seed of doubt seems to have been planted in certain scientist's minds, and hopefully the more open minded are really considering the possibility that ME/CFS research is flawed.
  15. Astrocyte

    Astrocyte

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    Hi Oceanblue,
    Like the vision of you as an excited puppy. Puppies tend to wee on the carpet when things get really exciting but I'm guessing that you dont have a problem with that. :D

    I wonder whether the scientific community haven't bothered critiquing ME psychological research cos they dont actually consider psychology proper science and therefore psychology papers are not worth bothering with?
  16. oceanblue

    oceanblue Senior Member

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    I was pretty excited about that letter but I'm relieved to report there were no accidents this time.

    You could be right about why psychological papers are not critiqued. The people who should be interested in critiquing them are fellow psychology researchers; I'm not sure if they lack the inclination or the skills. On another thread, someone quoted a book about virology research which stated that most participants apparently regard it as a 'combat sport' - savage criticism is the norm. Be nice to see some of that in this field too.

    Welcome to the forum.
  17. Dolphin

    Dolphin Senior Member

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    I'm not sure if the post by the reviewer has been linked to:
    http://www.bmj.com/content/320/7245/1343.full?sid=19f252e7-380a-4b97-9f3f-0470da038685
    (if that link doesn't so up, search the BMJ site for articles with author Pelosi in 2000)

    Anthony Pelosi has said some forthright things about ME and CFS over the years (perhaps particularly in the 1990s - I don't remember him much from the 2000s). He would be of the "Wessely school of thought". One has to wonder if his decision as a reviewer might have been different with a different group of individuals.
  18. oceanblue

    oceanblue Senior Member

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    Thanks, Dolphin, I hadn't seen that concluding correspondence. And how nice that the BMJ editor decided to invite everyone to dinner to celebrate their conclusion that it didn't matter after all.

    No one ever mentioned again the other errors that Bland pointed out in his initial critique
    Maybe that's why PACE felt at liberty to treat the CFQ as a normal distribution (it isn't, so 'mean-SD' should not be applied as they did, to define 'normal'). PACE didn't cite this Pawlikowska study, but did cite the 2010 Cella study which was based on the same underlying data and similarly was not normally distributed.
  19. Esther12

    Esther12 Senior Member

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    Thanks OB. I was just looking at some Wessely slides that had him presenting some of the data you picked apart here.

    It's a shame that we often don't get transcripts, so it's hard to bust them over it, as they may have been saying: "Here is a misleading graph that perfectly illustrates why CFS research needs to be viewed cautiously..."
    Valentijn likes this.

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