Discriminating between chronic fatigue syndrome and depression : a cognitive analysis - Core
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Psychological Medicine, 2001, 31, 469–479. Printed in the United Kingdom
" 2001 Cambridge University Press
Discriminating between chronic fatigue syndrome
and depression : a cognitive analysis
RONA M O S S - M O R R I S" KEITH J. P E T R I E
From the Health Psychology Research Group, Faculty of Medical and Health Science, The University of
Auckland, Auckland, New Zealand
ABSTRACT
Background. Chronic fatigue syndrome (CFS) and depression share a number of common
symptoms and the majority of CFS patients meet lifetime criteria for depression. While cognitive
factors seem key to the maintenance of CFS and depression, little is known about how the cognitive
characteristics differ in the two conditions.
Methods. Fifty-three CFS patients were compared with 20 depressed patients and 38 healthy
controls on perceptions of their health, illness attributions, self-esteem, cognitive distortions of
general and somatic events, symptoms of distress and coping. A 6 month follow-up was also
conducted to determine the stability of these factors and to investigate whether CFS-related
cognitions predict ongoing disability and fatigue in this disorder.
Results. Between-group analyses confirmed that the depressed group was distinguished by low
self-esteem, the propensity to make cognitive distortions across all situations, and to attribute their
illness to psychological factors. In contrast, the CFS patients were characterized by low ratings of
their current health status, a strong illness identity, external attributions for their illness, and
distortions in thinking that were specific to somatic experiences. They were also more likely than
depressed patients to cope with their illness by limiting stress and activity levels. These CFS-related
cognitions and behaviours were associated with disability and fatigue 6 months later.
Conclusions. CFS and depression can be distinguished by unique cognitive styles characteristic of
each condition. The documented cognitive profile of the CFS patients provides support for the
current cognitive behavioural models of the illness.
no clear distinguishing organic agent has been
INTRODUCTION
found (Evengard et al. 1999). The lack of a
Chronic fatigue syndrome (CFS) is a disorder of defining pathophysiology has led others to
uncertain aetiology, characterized by de- suggest that CFS is a somatic form of depression
bilitating fatigue which has been present for at (Manu et al. 1993).
least 6 months (Fukuda et al. 1994). The The argument for CFS as a form of depression
idiopathic nature of CFS has led to an ongoing is based on the significant overlap between these
debate as to the organic or functional aetiology two disorders. CFS shares a number of cardinal
of this disorder. Those favouring an organic symptoms with depressive disorders including
cause have linked CFS to viral pathogens, muscle extreme fatigue, sleep disturbance, diminished
abnormalities, and immunological and neuro- concentration, and problems with memory. In
logical changes. While a number of abnor- fact, up to 85 % of CFS patients report depressed
malities have been documented in CFS groups, mood as a key symptom (Komaroff & Buchwald,
1991) and around two-thirds of patients meet
" Address for correspondence : Dr Rona Moss-Morris, Health lifetime criteria for depression (Abbey, 1996).
Psychology Research Group, The Faculty of Medical and Health
Science, The University of Auckland, Private Bag 92 019, Auckland,
Studies comparing CFS patients to patients with
New Zealand. a range of medical illnesses, including rheu-
469470 R. Moss-Morris and K. J. Petrie matoid arthritis, multiple sclerosis, neuro- MacLeod, 1994). Thus, if CFS is distinct from muscular disorders and myopathies have in- depression, CFS patients should not report these variably reported significantly higher rates of classic errors of thinking. depression in CFS (Wessely & Powell, 1989 ; Our previous work has shown that CFS Katon et al. 1991 ; Wood et al. 1991 ; Pepper et patients appear to have a particularly negative al. 1993 ; Johnson et al. 1996). view of their illness and to be less likely to Despite this overlap, there is evidence that attribute their illness to internal factors when relevant differences may exist. Studies of the compared to patients with other chronic medical neuroendocrine system have demonstrated sig- conditions (Weinman et al. 1996). They also nificantly different physiological abnormalities tend to make catastrophic interpretations of the in each of these disorders, although results have consequences of their illness (Petrie et al. 1995). not always been consistent (Schwartz et al. Accordingly, we hypothesized that while de- 1994 ; Cleare et al. 1995 ; Goldstein et al. 1995 ; pressed patients ’ schema are dominated by Fischler et al. 1996). In addition, unlike de- negative self-perceptions, CFS patients ’ per- pressed patients, CFS patients do not seem to ceptions are dominated by their views of respond to antidepressant medication (Natelson themselves as seriously physically ill people. et al. 1996 ; Vercoulen et al. 1996). Therefore, we anticipated that while depressed A closer look at the psychological symp- patients would demonstrate negative distorted tomatology of these groups shows that CFS thinking in a range of situations, CFS patients patients consistently report lower mean scores would only demonstrate these distortions when on depression inventories, although their scores interpreting somatic information. are still within the depressed range (Hickie et al. Comparing CFS and depressed patients’ cog- 1990 ; Johnson et al. 1996 ; Wessely & Powell, nitions may not only help in differentiating the 1989). These differences are largely accounted phenomenology of the disorders. Recent models for by depressed patients scoring significantly of CFS suggest that patients’ cognitions play an higher on the self-reproach or cognitive important role in maintaining this disorder symptoms including feelings of guilt, low self- (Wessely et al. 1991 ; Surawy et al. 1995). In esteem, and suicidal ideation (Powell et al. 1990 ; particular, a precipitating event such as a virus is Johnson et al. 1996). seen to trigger a cycle of responses whereby A more detailed investigation of the cognitions patients interpret ongoing symptoms as signs of of the two groups may provide another avenue physical illness. This results in limiting activity to determine whether depression and CFS are levels and the development of cognitions and indeed distinct. Not only do cognitive symptoms behavioural responses which are thought to form part of the DSM-IV diagnosis of depression perpetuate the level of disability and fatigue but cognitive theories of depression suggest that experienced by these patients. To date, the specific thought processes define the disorder nature of CFS patients’ cognitions have largely (Beck, 1964). The characteristic cognitive profile been documented through clinical observation of depressed patients includes a negative self- and there is little empirical evidence to support concept, and themes of loss, abandonment and the unique nature of these belief structures. defeat (Beck, 1964). This negative self-schema is Thus, the aims of the current study were as thought to generate a series of distortions in follows. First, to compare the cognitions and thinking such as selective abstraction – focusing behavioural responses of CFS and depressed on the negative aspects of an experience, patients to determine whether these disorders catastrophising – expecting the worst outcome have unique cognitive profiles. In particular, we to occur, personalization – seeing oneself as hypothesized that CFS patients’ negative cog- responsible for negative events, and overgeneral- nitions would be specific to health and illness, izing – assuming the negative consequences of that they would have a tendency to view their one experience apply to another (Beck, 1964 ; illness as organic, and to limit their activity Beck et al. 1978). These distorted thought levels in order to cope with their illness. processes and negative self-concept distinguish Secondly, to investigate whether this cognitive depressed patients from patients with other profile remains stable over time and thirdly to forms of psychopathology (Mathews & determine whether the CFS-related cognitions
Cognitions in chronic fatigue syndrome 471
and behavioural responses predict ongoing The CIDI-Auto has demonstrated procedural
disability and fatigue in this disorder. validity against expert clinical diagnoses (Peters
& Andrews, 1993) and the items have good
METHOD reliability (Wittchen, 1994).
Participants Fourteen (26 %) of the 53 subjects had a
concurrent DSM-III-R diagnosis of major de-
Because of the phenomenological overlap be-
pression or dysthymia, similar to a number of
tween depression and CFS, an important com-
other studies which have identified concurrent
ponent of this study was ensuring the ap-
depression in CFS (Katon et al. 1991 ; Bom-
propriate allocation to groups. Standardized
bardier & Buchwald, 1995). In this study the
diagnostic interviews were used in conjunction
estimate of depression may have been con-
with self-report measures to confirm patient
servative, as the CIDI excludes somatic symp-
diagnoses. The CFS group was also divided
toms from diagnostic criteria if they have been
into those with and those without a concurrent
attributed to physical illness by a medical
diagnosis of depression, to avoid the possible
practitioner. As the role of somatic symptoms in
confounding of dual diagnoses.
diagnosing depression in CFS is a controversial
CFS group issue (Ray, 1991), the conservative estimate was
The CFS patients were recruited from a general deemed preferable. The final sample consisted of
medical practice specializing in the treatment of 39 CFS patients without depression (CFS) and
CFS. Patients aged between 18–65 who were 14 CFS patients with a concurrent diagnosis of
diagnosed by the general practitioner as having depression (CFS-depressed). Fifty-one per cent
CFS, and who provided informed consent to of this group belonged to a CFS support group.
participate in the study were interviewed by one The demographic details of the two CFS groups
of the investigators. Of the 65 patients who together with the comparison groups are pre-
provided informed consent, eight did not meet sented in Table 1. Analysis of variance
criteria, and four dropped out of the study. (ANOVA) and chi-square tests were used to
The diagnostic interview assessed whether confirm that the groups were comparable with
patients met current research criteria for CFS regard to demographic features.
(Fukuda et al. 1994) and whether they had a
concurrent diagnosis of depression. The inter- Depressed group
viewer-administered computerized version of the Inclusion criteria for the depressed group,
Composite International Diagnostic Interview included a current primary DSM-III-R diagnosis
(CIDI-Auto) (Health, WHO, 1993) was used to of major depression or dysthymia, a Beck
diagnose depression as it has been recommended Depression Inventory (Beck, 1978) score 10,
for use in CFS research (Fukuda et al. 1994). no evidence of psychosis, organicity, addiction,
Table 1. Characteristics of group participants
CFS CFS-depressed Depressed Healthy controls
(N l 39) (N l 14) (N l 20) (N l 38)
Gender, % Women (N) 82 (32) 85n7 (12) 65 (13) 74 (28)
χ# l 2n97, P l 0n40
Age, mean (..) 43n3 (12n7) 47 (12n07) 38n8 (12n5) 44n9 (10n8)
F l 1n64 ; df l 3, 107 ; P l 0n18
Tertiary qualified, % (N) 51 (20) 55 (11) 43 (6) 45 (17)
χ# l 4n1 ; P l 0n90
BDI scores, mean (..) 11n68 (5n45) 14n12 (6n02) 22n47 (6n7) 4n00 (2n47)
F l 61n74 ; df l 3, 107 ; P 0n001
Length of illness, mean (..) 8n9 (8n7) 7n8 (10n1) 14n1 (14n1)
F l 2n11 ; df l 2, 70 ; P l 0n13
Unemployed*, % (N) 59 (23) 57 (8) 30 (6)
χ# l 4n7, P l 0n09
* Unemployment due to illness.472 R. Moss-Morris and K. J. Petrie
and\or a current chronic illness. A score 10
Table 2. Current and past diagnoses of
on the BDI is indicative of possible depressive
depression across illness groups
disorder (Beck et al. 1978). Eight of the 46
CFS CFS-depressed Depressed healthy volunteers scored 10 on the BDI
(N l 39) (N l 14) (N l 20) resulting in a final sample of 38 healthy controls.
% (N) % (N) % (N)
Measures
Current diagnoses
No diagnosis 100 (53) Two types of measures were included in this
Major depression 85n7 (12) 90 (18) study, those measuring cognitive behavioural
Dysthymia 14n2 (2) 10 (2)
factors and those assessing the specific symptom
Past history
No history 42n1 (16) 14n3 (2) 10 (92) profiles and level of disability of the groups.
Major depression 50 (19) 78n6 (11) 85 (17)
Dysthymia 7n9 (3) 7n1 (1) 5 (1) The Self-Esteem Scale (Rosenberg, 1995)
This was used to operationalize negative self-
schema. It is the most frequently used measure
or chronic physical illness. To be comparable of self-esteem and has good internal reliability,
with the CFS group, the depressed patients test–retest reliability, and convergent and dis-
needed to be receiving out-patient rather than criminate validity (Blascovich & Tomaka, 1991).
in-patient treatment and to be between 18- and High scores represent greater self-esteem.
65-years old. Patients were recruited through
private psychologists and community mental Self-rated health
health centres. Subjects who provided informed Self-rated health was used as a measure of illness
consent were interviewed with the CIDI to schema. It is a widely used single-item measure
confirm that they met current criteria for a of individuals’ perceptions of themselves as
depressive disorder. Three of 23 patients inter- healthy or sick people (Johnston et al. 1995).
viewed did not meet inclusion criteria. The final The Short Form Health Survey version of the
primary depressed group consisted of two scale (Ware & Sherbourne, 1992) was used in the
patients with dysthymia and 18 with major current study, where low scores represent more
depression. healthy perceptions.
The CIDI data from all three patient groups
are presented in Table 2. Most of the CFS- Illness Perception Questionnaire (IPQ,
depressed and primary depressed patients met Weinman et al. 1996)
criteria for major depression with only two Two subscales of the IPQ were used to measure
patients in each group meeting criteria for dimensions of patients’ illness beliefs. The illness
dysthymia. The majority of the patients had a identity subscale measures the number of so-
history of depressive disorders, including 68 % matic symptoms patients associate with their
of the non-depressed CFS patients. illness. The identity scale in this study consisted
Table 1 shows that the mean BDI score for of 20 symptoms, including the 12 core IPQ items
the primary depressed group was in the mod- which are symptoms commonly experienced by
erately depressed range (Kendall et al. 1987) and the general population and eight additional
was substantially higher than the scores for the symptoms commonly reported by depressed and
two CFS groups. The means for the CFS groups CFS patients (Moss-Morris et al. 1996). The
both fell within the mildly depressed range, causal subscale measures patients’ beliefs about
although the score for the CFS-depressed group the causes of their illness. For the purpose of this
was higher than that of the CFS group. study patients were presented with a list of 18
possible causes of their illness. Half of these
Control group were psychological causes such as ‘recent stress-
The healthy controls were recruited through the ful events’ and ‘my mental attitude ’ while the
university and the community on the basis that other half were physical causes such as ‘a virus’,
they matched the patient groups as far as possible ‘immune dysfunction ’ or ‘a neurochemical im-
for the demographic features identified in Table balance ’. Subjects were asked to assign a
1. Exclusion criteria were a BDI score 10, a percentage to each factor, so that the overall
current or past history of depression or CFS, assignment of causes equalled 100 %. If theyCognitions in chronic fatigue syndrome 473
believed the factor was unrelated to their illness
they were asked to assign the factor 0. Two Symptoms of distress and fatigue
scores were computed, one which measured the Two subscales of the Mental Health Inventory
percentage patients assigned to physical causes (Viet & Ware, 1983) that discriminate between
and the other the percentage assigned to psycho- the somatic and affective components of distress
logical causes. were used to substantiate the symptom dif-
ferences between the four subject groups. The
Cognitive Errors Questionnaire-Revised MHI-5 (Ware et al. 1993) is a measure of the
(CEQ-R, Moss-Morris & Petrie, 1997) affective dimensions of anxiety, depression, and
The CEQ-R was devised specifically to assess psychological well-being. It has demonstrated
cognitive distortions in this study. The CEQ-R high internal consistency (Ware et al. 1993), and
is divided into two subscales : the 12-item is a valid measure of psychiatric dysfunction
General CEQ-R and the 9-item Somatic CEQ- (Berwick et al. 1991). The Vitality Scale (Ware et
R. Each of the 21 items describes an everyday al. 1993) is a 4-item measure of energy and
situation involving either work, recreation, or fatigue. The vitality scale has a sound record of
family experiences. The general items focus on empirical validity, item discriminant validity,
interpersonal experiences, while the somatic ones and scale reliability (Ware & Sherbourne, 1992).
include the experience of common symptoms, Both of these subscales are scored so that high
such as fatigue, aches and pains, and muscle scores indicate greater psychological well-being
weakness. These vignettes are followed by a and vitality.
thought that a person in that situation may
have. For example, one of the general items Disability
states ; ‘ You hand in a report to your boss that The Sickness Impact Profile (SIP, Gilson et al.
has taken you four hours to write. Your boss, 1979) was used as a measure of sickness related
however, doesn’t say anything about it. You disability. The SIP has been found to be a
think to yourself, ‘‘ (S)he must think I did a lousy convincing measure of functional status in a
job ’’ ’. An example of a somatic item is ‘You range of chronic illnesses (De Bruin et al. 1992).
have been feeling very weak and tired of late, but The questionnaire’s validity, test–retest re-
have continued to work. Although you got quite liability and internal consistency are well es-
a bit done today, you finished work early because tablished (De Bruin et al. 1992). Because the
you were feeling particularly exhausted. You scale is very lengthy and the reliability and basic
think to yourself, ‘‘What a terrible day. It seems construct validity appear to be unaffected by
like I can’t get anything done ’’ ’. The thoughts administering only selected subscale categories
are worded to represent the cognitive errors of (Bergner et al. 1981), six subscales were includ-
catastrophizing, overgeneralizing, personali- ed in the current study. Five of these
zation, and selective abstraction (Beck et al. subscales – social interaction, alertness behav-
1978). An in depth analysis of this questionnaire iour, sleep and rest, home management, and
which included the current samples showed that recreational pastimes – have been shown to
the subscales have high internal consistency most clearly represent CFS-related disability
across groups and good test–retest reliability (Schweitzer et al. 1995). These scores were
over 6 months (Moss-Morris & Petrie, 1997). summed and divided by five to produce a SIP
dysfunction score out of 100. We also included
Coping the SIP work subscale as a separate variable as
A three-item measure of limiting coping was it was only relevant to the percentage of people
included in the questionnaire (Sharpe et al. who were working before their illness.
1992). Patients were asked the extent to which
they limited exercise, activity, and stress in order Procedure
to cope with their illness on a 4-point scale rated Items determining the demographic features of
from ‘I usually didn ’t do this at all ‘to ’ I usually the groups and the self-report measures were
did this a lot ’. These items have been shown to compiled into a single questionnaire. The IPQ
predict ongoing disability in patients with subscales, SIP, and limiting coping scale, which
chronic fatigue (Sharpe et al. 1992). are specific to illness, were included only in the474 R. Moss-Morris and K. J. Petrie
patient questionnaires. All participants provided one and P 0n007 (0n05\7) at time two. To
informed consent before they were given a copy ascertain whether covariates should be included
of the questionnaire and a self-addressed return in these equations, correlations were computed
envelope. The patient groups also completed a between age, gender, level of education, marital
diagnostic interview to determine their eligibility status, length of illness, and the various de-
for the study. All subjects were asked to complete pendent variables (DVs). There were no sig-
the questionnaire within a week and to post it nificant correlations, and as there were no
back to the investigators. significant differences between the groups on
Six months after completing the initial ques- these factors, no covariates were included. Post-
tionnaire, participants in the patient groups hoc analyses were conducted with Tukey’s test.
completed a shortened version of the ques- Stepwise multiple regression was used to in-
tionnaire included the MHI-5, Vitality, SIP, vestigate the relationships between the cognitive
Self-Rated Health, CEQ-R and Illness Identity behavioural factors and ongoing disability and
scales. Two of the depressed patients could not fatigue in the CFS group.
be contacted and one depressed patient and two
Symptoms and disability across groups
CFS patients did not return the questionnaire.
The overall response rate of the follow-up A summary of the ANOVA results from time
questionnaire was 85 % for the depressed group, one are presented in Table 3. The first stage of
95 % for the CFS group and 100 % for the CFS- the analyses involved clarifying the validity of
depressed group. the four groups by comparing their scores on the
MHI-5 and Vitality scales. Vitality scores were
significantly different between groups. Post-hoc
RESULTS
tests suggested that this difference was due to the
Data analysis was performed on the SPSS higher scores for the control group when
version 8.0 computer software program compared to all three patient groups, who had
(Norus) is, 1993). Results of the evaluation of the equivalent scores. MHI-5 scores also differed,
assumptions of normality of sampling dis- with post-hoc analyses suggesting a number of
tributions, linearity, and homogeneity of vari- significant contrasts between the four groups.
ance were satisfactory for all of the variables As with the Vitality scale, healthy controls
and there were no obvious outliers. A series of scored significantly higher on the MHI-5 than
Analysis of Variance (ANOVA) were used to all the patient groups. CFS non-depressed
test the hypotheses regarding differences between patients also scored significantly higher than
the groups. Due to the large number of planned both the depressed groups and CFS-depressed
analyses, a Bonferonni adjusted alpha was used patients scored higher than primary depressed
in these equations ; P 0n0045 (0n05\11) at time patients.
Table 3. Analysis of variance of the self-report measures at Time 1
CFS CFS-depressed Depressed Controls
Mean (..) Mean (..) Mean (..) Mean (..) df F
Vitality 26n54 (18n54)† 20n71 (18n69)† 26n50 (14n96)† 68n69 (15n14) 3,107 55n46*
MHI-5 68n10 (15n60)†‡ 47n43 (3n75)†‡§ 36n40 (15n57)† 79n58 (10n26) 3,107 51n05*
SIP dysfunction 42n17 (13n79) 47n59 (14n14) 44n82 (13n82) 2,67 0n83
SIP work 58n48 (17n48) 59n69 (33n64) 52n29 (24n94) 2,54
Self-esteem 31n25 (4n73) 27n71 (5n67)†§ 24n86 (5n76)†§ 33n11 (4n12) 3,107 14n85*
Self-rated health 4n05 (0n79)†‡ 4n00 (0n96)†‡ 3n15 (1n14) 1n76 (0n68) 3,107 52n86*
General CEQ-R 21n69 (8n99)‡ 26n03 (7n79)‡ 35n15 (11n85)† 21n47 (6n58) 3,107 10n66*
Somatic CEQ-R 21n79 (8n16)† 21n36 (6n22)† 23n24 (9n1)† 14n83 (4n65) 3,107 12n97*
Somatic illness identity 17n59 (2n20)‡ 18n21 (2n33)‡ 13n40 (3n94) 2,70 17n82*
Psychological attributions 25n39 (24n99)‡ 17n86 (21n81)‡ 62n13 (23n42) 2,68 19n31*
Physical attributions 62n11 (28n62)‡ 77n86 (21n81)‡ 15n90 (16n12) 2,68 31n04*
Limiting coping 9n87 (1n80)‡ 8n79 (2n61)‡ 7n05 (2n48) 2,70 11n04*
* P 0n0045.
† Significantly different from the control group.
‡ Significantly different from the depressed group.
§ Significantly different from the CFS group.Cognitions in chronic fatigue syndrome 475
The ANOVA of the SIP data showed there
were no differences in the level of sickness Coping
related disability reported by all three groups. As predicted, both CFS groups were more likely
Thus, in terms of presentation, CFS and de- to deal with their illness by limiting activity and
pressed patients appear to report equivalent stress than were the depressed group. There was
levels of energy loss and disability. Depressed no difference on this measure between the CFS
patients however report higher levels of negative groups.
mood than do CFS patients.
Stability of cognitions over 6 months
Cognitive behavioural factors across groups Identical analyses were conducted on the
Self-esteem measures included in the second questionnaire.
Comparisons confirmed that the two depressed Table 4 shows that there was almost no change
groups had significantly lower self-esteem than in the pattern of results. The three groups were
the CFS non-depressed and healthy control still indistinguishable on measures of vitality
groups. There were no significant differences and sickness-related disability. Both the de-
between the two depressed groups, or between pressed groups scored lower on psychological
the CFS non-depressed and healthy control well-being (MHI-5) than did the CFS group.
groups. However, unlike at time one, the CFS-depressed
group did not score significantly higher than the
Self-rated health depressed group on this scale. Both of these
The ANOVA for self-rated health showed that groups scored higher on this scale than at time
both CFS groups rated themselves as signifi- one, suggesting that their mood had improved
cantly less healthy than depressed patients and over the 6-month period.
controls. In turn, the depressed group also rated The prototype of cognitive differences was
themselves as less physically healthy than unchanged. The CFS groups rated themselves as
controls. less healthy and experiencing more physical
symptoms as part of their illness. The depressed
Illness beliefs group scored higher on the General CEQ-R but
Both CFS groups showed a significantly stronger not the Somatic CEQ-R. Interestingly, although
somatic illness identity as they endorsed a higher the groups showed improvements in their levels
number of physical symptoms to their illness of disability and symptom reports over the 6-
than did depressed patients. There was no month period, within-group analyses showed
differences between the two CFS groups on this that there were no significant changes in scores
measure. Similarly, the two CFS groups made on the CEQ-R subscales in either of the groups.
significantly more physical attributions and For the CFS group the results of the paired
significantly fewer psychological attributions for samples t tests on Somatic CEQ-R were t l 0n83
their illness than did depressed patients. (50) P l 0n41 and on the General CEQ-R, t l
k0n74 (50) P l 0n46. For the depressed group
Cognitive distortions the results on the Somatic CEQ-R were t l
To assess whether level and type of cognitive k0n16 (16) P l 0n88 and on the General CEQ-
distortion varied with group membership, the R, t l 0n47 (16) P l 0n64.
two subscales of the CEQ-R were entered into
two separate ANOVA equations. There was a Cognitive-behavioural variables and ongoing
highly significant difference for group on both disability and fatigue in CFS
subscales. Post-hoc analyses revealed that the Three separate stepwise regression equations
depressed group scored significantly higher than were used to investigate the relationships be-
all the other three groups on the General CEQ- tween the CFS-related cognitive-behavioural
R. There was no difference between the two CFS factors measured at time one, and disability and
groups and healthy controls on this subscale. fatigue measured 6 months later in the CFS
However, all three patient groups scored signifi- group. The dependent variables included the
cantly higher on the somatic CEQ-R when Vitality scale as a measure of fatigue and the two
compared with healthy controls.476 R. Moss-Morris and K. J. Petrie
Table 4. Analysis of variance of the self-report measures at 6 months follow-up
CFS CFS-depressed Depressed
Mean (..) Mean (..) Mean (..) df F
Vitality 30n14 (21n97) 30n36 (18n76) 41n18 (18n50) 2,65 1n82
MHI-5 69n62 (13n77) 56n57 (15n11)‡ 52n00 (25n38)‡ 2,65 6n85*
SIP dysfunction 37n03 (17n87) 37n50 (17n05) 26n93 (16n21) 2,65 2n27
SIP work 46n95 (26n18) 34n80 (28n32) 41n03 (25n71) 2,53 1n04
Self-rated health 3n59 (0n83)† 3n71 (0n83)† 2n76 (0n90) 2,65 6n67*
General CEQ-R 22n84 (11n53)† 24n71 (9n29)† 33n29 (11n11) 2,65 5n34*
Somatic CEQ-R 21n65 (9n10) 22n50 (4n60) 23n49 (9n66) 2,65 0n27
Somatic illness identity 17n03 (4n54)† 17n00 (3n38)† 9n50 (6n10) 2,65 17n64*
* P 0n007.
† Significantly different from the depressed group.
‡ Significantly different from the CFS group.
SIP variables, general dysfunction and work The symptom profiles of each of the patient
disability. groups to some extent reflected the differences in
In each of the equations, age and length of these self-schemas. The groups were clearly
illness were entered as independent variables delineated on the affective dimension of psycho-
together with physical attributions, somatic logical well-being with the primary depressed
illness identity, the Somatic CEQ-R, and limiting patients being the most distressed and the
coping. For vitality, both somatic illness identity healthy controls the least distressed. CFS
and age entered the equation and accounted for patients fell in between these groups with the
a unique 21 % of the variance, F (1,41) l 12n52, CFS-depressed patients reporting more distress
P 0n001). Somatic illness identity was the than the non-depressed ones. The three patient
strongest predictor (β l k0n48, P 0n001) fol- groups were indistinguishable on the somatic
lowed by age (β l 0n31, P 0n05). Somatic illness dimension of distress, with all three groups
identity (β l k0n61, P 0n001) and the Somatic reporting substantially lower levels of vitality
CEQ-R (β l 0n26, P 0n05) were the only sig- than healthy controls.
nificant predictors of dysfunction. Together With regard to illness beliefs, there were no
these variables accounted for 38 % of the differences between the two CFS groups, but
variance in dysfunction, F (1,41) l 24n60, substantial differences between CFS and de-
P 0n001. Somatic illness identity (β l 0n56, pression. In accordance with previous research,
P 0n001) was once again the first variable to CFS patients made significantly more physical
enter the equation for work dysfunction with attributions but fewer psychological attributions
limiting coping (β l 0n51, P 0n001) also a for their illness than did depressed patients
significant predictor. Taken together these two (Powell et al. 1990). Both CFS groups also
variables accounted for a unique 24 % of the ascribed a significantly larger number of somatic
variance in work dysfunction, F (1,32) l 10n32, symptoms to their illness than did the depressed
P 0n01. group. While this difference may merely reflect
the physical status of the CFS patients there are
DISCUSSION
arguments against this possibility. Earlier work
The results generally supported the hypothesis has shown that CFS patients ascribe a larger
that depressed patients’ self-schema are domin- number of somatic symptoms of their illness
ated by a negative view of the self, while CFS than do patients with other chronic medical
patients are primarily concerned with their poor conditions (Weinman et al. 1996). In the current
health. Both depressed groups had lower self- study, out of a total of 20 symptoms, the CFS
esteem than healthy controls and CFS non- patients on average reported experiencing 18 as
depressed patients, while both CFS groups rated a result of their illness. While some of these
themselves as significantly less healthy than the symptoms such as fatigue and muscle pain are
other two groups. The primary depressed characteristic of CFS, others such as pins-and-
group’s ratings of health lay midway between needles and sore eyes are symptoms commonly
those of controls and the CFS groups. experienced in the population as a whole. ThisCognitions in chronic fatigue syndrome 477
suggests that CFS patients may misattribute which encourage rather than limit activity, may
common symptoms to their illness. help to alleviate some of the negative disabling
CFS patients’ preoccupation with their effects of the illness. It may be particularly
symptoms rather than with their sense of self is important to explore alternative labels for
also reflected in the CEQ-R data. CFS patients symptoms. For instance, some of the somatic
only displayed distorted thinking in situations symptoms patients attribute to their CFS could
where they might experience symptoms and not be re-labelled as signs of deconditioning, while
in general interpersonal situations. Concurrent others such as headaches could be attributed to
depression did not appear to alter this pattern of stress. It appears to be less important to alter
thinking. Only the depressed group could be patients’ beliefs that their illness is caused by
distinguished from the healthy controls on the physical factors. This factor may in fact be
tendency to distort the meaning of interpersonal adaptive in that it may help to maintain a
situations. It is interesting that although the healthy self-esteem.
depressed patients do not view their health as Taken together, the results of this study are
negatively as the CFS group, and do not respond consistent with a growing body of evidence that
to their illness by limiting stress and activity to argues against CFS being a version of de-
the same extent, they have a similar tendency to pression. It also provides some support for the
report somatic errors in thinking. For this group, role cognitions and behaviour play in the
somatic errors may be reflective of a generalized maintenance of CFS. However, a limitation of
tendency to see the world in a negative fashion. the current study was the small sample sizes
The differences between CFS and depression and the convenience sampling method make it
were maintained over the 6 month period. There difficult to generalize the results to all CFS and
were no significant changes in the scores on depressed patients. It is also difficult to confirm
either the Somatic or General CEQ-R, sug- the directional links of these models from this
gesting that these may be relatively stable comparative study. It is possible that the
thought processes or ways of viewing the world. cognitive profile in CFS is a reflection of the fact
It is also worth noting that CFS-depressed that these patients have a serious ongoing
patients showed greater overlap with CFS physical illness. However, two findings argue
patients than with primary depressed patients at against this possibility. First, CFS patients
both time points. appear to have even more negative views of their
In support of the cognitive behavioural illness than do patients with other chronic
models, the CFS-related cognitive behavioural physical illnesses and these beliefs are associated
factors predicted ongoing disability and fatigue with ongoing disability and fatigue. Secondly,
in this group, even when controlling for age and although numerous physiological abnormalities
length of illness. Somatic illness identity was the have been documented in CFS, these are seldom
most significant predictor of both ongoing associated with the magnitude of the symptoms
dysfunction and fatigue. Coping by limiting experienced by CFS patients (Wessely, 1996).
stress and activity was associated with work- Prospective research in this area and studies that
related dysfunction, while somatic cognitive compare CFS patients to patients with other
errors were associated with disability in the physical illnesses could help to address the nature
other domains. Interestingly, consistent with of CFS patients’ cognitions further.
previous work in this area (Moss-Morris et al.
1996 ; Heijmans & de Ridder, 1998), physical This research was supported by the Health Research
attributions which are one of the key defining Council of New Zealand.
features of the illness, failed to predict outcome
in this group. Changes in physical attributions
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