Cognitive deficits in CFS vs major depression and healthy controls

Dolphin

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New Belgian study

Cognitive deficits in patients with chronic fatigue syndrome compared to those with major depressive disorder and healthy controls.

Clin Neurol Neurosurg. 2011 Jan 19. [Epub ahead of print]

Constant EL, Adam S, Gillain B, Lambert M, Masquelier E, Seron X.

Department of Psychiatry, Universit Catholique de Louvain, 1200 Brussels, Belgium.

Abstract

OBJECT: Chronic fatigue syndrome (CFS) patients report usually cognitive complaints. They also have frequently comorbid depression that can be considered a possible explanation for their cognitive dysfunction. We evaluated the cognitive performance of patients with CFS in comparison with a control group of healthy volunteers and a group of patients with MDD.

PATIENTS AND METHODS: Twenty-five patients with CFS, 25 patients with major depressive disorder (MDD), and 25 healthy control subjects were given standardized tests of attention, working memory, and verbal and visual episodic memory, and were also tested for effects related to lack of effort/simulation, suggestibility, and fatigue.

RESULTS: Patients with CFS had slower phasic alertness, and also had impaired working, visual and verbal episodic memory compared to controls. They were, however, no more sensitive than the other groups to suggestibility or to fatigue induced during the cognitive session. Cognitive impairments in MDD patients were strongly associated with depression and subjective fatigue; in patients with CFS, there was a weaker correlation between cognition and depression (and no correlation with fatigue).

CONCLUSIONS: This study confirms the presence of an objective impairment in attention and memory in patients with CFS but with good mobilization of effort and without exaggerated suggestibility.

Copyright © 2011 Elsevier B.V. All rights reserved.
 

Dolphin

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Suggestibility bit (only annoying bit)

There is basically only one bad bit (IMO) in this paper:
3.5. Subject’s response to suggestibility Concerning suggestibility, a univariate ANOVA on the suggestibility index revealed a tendency for a significant main group effect; post hoc analysis showed only a tendency for patients with MDD to be more suggestible than patients with CFS. Within the CFS group now, we also observed a positive correlation between length of illness and the suggestibility index (r = .4518; p = .023) ; suggesting that the longer these patients had had CFS, the more open they were to suggestion.
(I'm not sure why they use the second tendency - table shows its statistically significant i.e. MDD are more suggestible than patients with CFS.

(from Discussion)
Suggestibility refers to a type of information processing that is selective and distorted in that relevant information cannot be handled in a balanced fashion. According to DiClementi et al. [29], “suggestible persons with CFS do experience the symptoms they report. However, a tendency to focus on symptoms, perhaps to the exclusion of other information, may be related to CFS patients’ difficulties in processing complex cognitive information, and difficulties with divided attention” (pp. 684–685). In line with this argument, it is important to note that although, in our study, patients with CFS were not more suggestible than the two other groups, there was a positive correlation between length of illness and the suggestibility index. This may mean that the longer the CFS illness, the more patients focus on their symptoms and if someone else focuses their attention on their symptoms, they will show a greater response to that suggestion and this process will impair the realization of the cognitive task in which they are involved.
Background:
A suggestibility index (total score of PASAT 2 minus total score of PASAT 1) was calculated and compared among the groups using an ANOVA. A higher negative index indicated a greater deterioration of scores on PASAT 2 and thus a greater response to suggestibility.
Suggestibility index
CFS: −.44 (4.18)
DG: −2.6 (3.30)
CG: −1.24 (1.9)
DG: depressed group; CG: control group
F(2,72) =2.8≈ (≈ represents p<1.0 and >.05;
CG/DG =.15
CG/CFS =.39
DG/CFS * (* represents p<.05)
So the CFS group had the lowest scores i.e. were the least suggestible
This could be relevant to the point they make.
There could be a correlation in the CFS group but still all or nearly all CFS wouldn't qualify as being suggestible as they were starting from a "low base" (SD does suggest there is a little bit of a spread in the CFS group).
There is no threshold given to define what is suggestible. So there may be a correlation but it may be of no clinical relevance.
One explanation might be that being reminded that they were tired alerted them (people who had the illness longer) more that they needed to "ease back the throttle a little" - the more time one has the illness, the more time one has had to learn this/the more times it has been re-inforced from experience not to push one's body to its limits if one is feeling tired, the way a healthy person can without ill-effect.

I am not sure why there might be this correlation with length of illness.
They did also find the following:
For the working memory tasks, CFS patients had longer median times and fewer correct responses than controls on the working memory (TEA) and a tendency for lower total scores on the PASAT. It is also interesting to note that for the working memory (TEA)there was a negative correlation between median time and length of illness (r =−.4563; p = .022) and between correct responses and length of illness (r =−.4331; p = .031), suggesting that the longer the duration of the CFS, the more impaired the patients were on this cognitive test.
 

Esther12

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Thanks for posting your thoughts on this.

I've not looked atthe paper, but is it possible that suggestability is related to things like 'a sense of self-worth'/insecurity/etc?

Living with a chronic illness can knock people's self-confidence, and I expect that this would affect what I understand 'suggestability' to be (although I find these terms often mean different things in an academic context than in every day speech).
 
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So the CFS group had the lowest scores i.e. were the least suggestible
Much as I like the finding, I think the whole 'suggestibility' thing is chasing shadows. Measuring a test in two parts and seeing if performance in the second part is worse after suggesting to the patient they might be fatigued could mean something if they had used a control of patients where no suggestion was made. But they didn't do this.

I am not sure why there might be this correlation with length of illness.
Given the large number of dependent variables they used (24) they should have made some adjustment for repeated measures and they don't appear to have done - the significance threshold should have been higher than 95% and so things like the correlation with illness length (which was yet another comparison) probably wasn't really significant. Looks more like data trawling to me.
 
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Measuring a test in two parts and seeing if performance in the second part is worse after suggesting to the patient they might be fatigued could mean something if they had used a control of patients where no suggestion was made. But they didn't do this.
Right. Otherwise, it is probably just reversion to the mean, given the lower level of suggestibility to start with.
 

Dolphin

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Right. Otherwise, it is probably just reversion to the mean, given the lower level of suggestibility to start with.
Don't think reversion (regression) to the mean applies in this case. This was a correlation with length of illness rather than a two stage test where the second test was closer to the mean than the former.
 

Dolphin

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Much as I like the finding, I think the whole 'suggestibility' thing is chasing shadows. Measuring a test in two parts and seeing if performance in the second part is worse after suggesting to the patient they might be fatigued could mean something if they had used a control of patients where no suggestion was made. But they didn't do this.
Could be. Just to clarify, I wasn't particular excited by the CFS group having the lowest suggestibility overall, just using it in one possible "defence" from the point they were making.
 
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Don't think reversion (regression) to the mean applies in this case. This was a correlation with length of illness rather than a two stage test where the second test was closer to the mean than the former.
I'm thinking of it in a different way, as if the resuts from those with longer illness lengths wasn't actually due to the illness length, but rather an artifact of repeating the test. The slope itself might be just a coincidence.

You are right, that it is hard to tell unless a repeat test is done.
 

laura

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New Belgian study
Thanks for sharing, Dolphin! Very interesting study.
I think even more than the fatigue, the cognitive symptoms are the hardest for me.

Still being compared to people with depression, though, makes me want to scream. Are we STILL at square one, trying to prove CFS is not a mental illness?! And that our symptoms are not psychosomatic ("suggestibility")?! Arg.

I want more studies on treatments for the cog. symptoms.