Journal of Psychosomatic Printed in Great Britain.

ILLNESS

Research,

Vol. 36, No. 3. pp. 243-256,

1992. 0

PERCEPTION CHRONIC

0022-3999/92 $5.00+.00 1992 Perganlon Press plc

AND SYMPTOM COMPONENTS FATIGUE SYNDROME

IN

C. RAY,* W. R. C. WEIR,? S. CULLEN* and S. PHILLIPS* (Received

4 June

1991; accepted

in revised form

28 August

1991)

Abstract-Two-hundred and eight patients with chronic fatigue syndrome (post-viral fatigue syndrome) completed a questionnaire which dealt both with their illness in general and with the extent to which they experienced specific symptoms. A factor analysis of the symptom data yielded four components: emotional distress; fatigue; somatic symptoms; and cognitive difficulty. Emotional disturbance is a common feature of the disorder and its role has been widely debated. When the symptom components were considered independently, fatigue, somatic symptoms and cognitive difficulty were associated with questionnaire items relating to general illness severity, but emotional distress was not. Thus negative emotions did not contribute directly to patients’ perception of illness severity. They were, however, correlated with the other symptom components. It is argued that this correlation reflects a reciprocal influence, with negative emotions exacerbating fatigue and other key symptoms and the debilitating nature of these symptoms enhancing emotional vulnerability.

INTRODUCTION

THE CHIEF characteristic of chronic fatigue syndrome, as the term implies, is prolonged and excessive fatigue or fatigability; this may be accompanied by difficulties in concentration, memory and other cognitive functions, by disturbances of mood, and by a range of somatic symptoms [ l-61 . The disorder is also referred to as post-viral fatigue syndrome (PVFS) and myalgic encephalomyelitis (ME). Its aetiology currently remains obscure and may prove to be complex: in these circumstances, chronic fatigue syndrome (CFS) has the advantage of being an umbrella term which highlights the principal symptom without making assumptions about aetiology. While there is evidence of persistent viral involvement [ 7-101 and of immunological abnormalities [ 1 l-15 ] in some patients, the aetiological significance of these findings has yet to be established. The role of psychological factors has also been much debated [ 16-211 . Several studies have found relatively high rates of psychiatric disorder, especially major depression, together with elevated scores on self-report scales of psychological distress [22-271. These findings are open to various interpretations [28, 291. On the one hand, they may be taken to indicate that symptoms are part of an essentially psychological disorder. A variant of this hypothesis is that an acute, possibly infective, illness precipitates fatigue, but that cognitive and emotional factors then maintain avoidant behaviour and result in the prolongation of symptoms once the initial problem has been resolved [ 30, 3 1 ] . On the other hand, rather than contributing to the illness, it is possible that emotional disturbance is primarily an outcome, and that it functions either as a direct symptom alongside

*Department of Human Sciences, Brunel University. tcoppetts Wood Hospital, The Royal Free Group. Address correspondence to: Dr C. Ray, Department of Human Middlesex UB8 3PH. U.K. 243

Sciences,

Brunei University,

Uxbridge,

244

C. RAY et al.

other symptoms or as a reaction to fatigue and disability. The temporal relationship between psychiatric disorder and the onset of fatigue has been examined in an attempt to clarify the causal basis of their association. A proportion of patients report that psychiatric disorder preceded their fatigue [ 23, 321 , and a relatively high rate of premorbid depression has been noted in comparison with controls [26] . Such findings suggest that psychiatric illness may be an antecedent risk factor for some patients. However, retrospective data should be interpreted with caution, especially in the context of a long term illness which may not have a clearly demarcated onset. Furthermore, one study has found rates of premorbid depressive illness and total psychiatric disorder similar to those in the general population [ 221 ; the authors concluded that psychiatric disturbance is likely to be a consequence of fatigue. The status of psychological and other, putative causal factors is thus ambiguous, and this ambiguity is paralleled by difficulties in defining the syndrome. There is as yet no ‘gold standard’ against which the identification of cases can be validated [ 331. This, together with the syndrome’s complexity, has led researchers to propose somewhat different definitional criteria [ 34-361. The CDC case definition [ 31 requires two major criteria to be fulfilled: fatigue or easy fatigability, for a period of at least six months, which impairs daily activity to a level below 50% of the premorbid activity level, together with the exclusion of other clinical conditions. Additionally, patients should meet a specified number of minor symptom and physical criteria. This definition has met with some criticism, and an alternative set of guidelines has been proposed [ 371. The criteria for chronic fatigue syndrome are that fatigue should be the principal symptom, have a definite onset, be severe and disabling, and be present for a minimum of six months and present for more than 50% of the time. Other symptoms may be present, such as myalgia, and mood and sleep disturbance, but they are not necessary features. Established medical conditions, and some psychiatric disorders, are grounds for exclusion. In the absence of a clear diagnostic marker, it is difficult to determine how limiting a definition should be. There are obvious advantages in identifying a homogeneous group of patients for research purposes; however, too specific a stipulation of minor criteria at this stage may impose an artificial constraint. The present study focused upon variations within the patient sample. The first objective was to explore by factor analysis the structure of symptoms reported; they could then be described in terms of a reduced set of dimensions. The second was to examine the relationships between these symptom components and patients’ global perceptions of the illness. Referring to variations within the ongoing illness, it has been suggested that affect plays an important role in the perception of severity [ 381. One of the components to emerge in this study comprised emotional distress, and its relationship with other variables was of particular interest in view of controversy about the role of psychological factors. METHOD The sample The data were obtained from a postal questionnaire completed by a hospital out-patient sample. These patients had received a diagnosis of post-viral fatigue syndrome, and their condition was being regularly monitored at a specialist clinic. The diagnostic criteria employed have been discussed elsewhere [ 391

Symptom

components

in CFS

245

In addition to the exclusion of other conditions, patients were required to meet two major criteria: (1) persistent or, occasionally, relapsing lethargy lasting for at least six months, with professional or social life, or both, being completely curtailed as a result; (2) exercise-induced muscle fatigue precipitated by trivially small exertion relative to the patient’s previous exercise tolerance. Minor criteria giving support to the diagnosis comprised autonomic, neuropsychiatric and immunologically-relevant symptoms, with qualifying symptoms from two separate categories being highly suggestive of the diagnosis. Relevant physical signs were pharyngitis, tender enlargement of the lymph nodes and muscle tenderness. The absence of these physical signs did not, however, exclude the condition. The questionnaire One section of the questionnaire comprised a comprehensive list of symptoms, including emotional responses, which have been linked with the disorder. These were worded to be easily understood by the layperson. Patients were asked to rate the extent to which they had experienced each of these within the past month, using a scale ranging from 0 (not at all) to 4 (extremely). Other sections of the questionnaire covered a number of areas relating to patients’ perceptions of the general illness; these included its initial onset, its current severity and variability, and perceived causes and outcomes. For the majority of these questions, patients were required to select a response from a range of predetermined, ranked alternatives. In addition, they were invited to comment in their own words on their illness experience. Several drafts of the questionnaire were piloted in clinic, and questions and response formats revised accordingly. The final questionnaire was posted to 264 patients. The response rate was relatively high, with 84% returning completed questionnaires; excluding 14 late returns, 208 questionnaires were available for analysis.

ANALYSES

Characteristics

AND

RESULTS

of the respondents

There was an excess of females and a positive socio-economic gradient, as has been reported in similar samples; 69% were female, and a high proportion (40%) had been educated to degree level or equivalent. At the time of the study, 20% were in full time work and 17 % in part time work; 75 % of those who were not working, or who were working part time, said that this was because of their illness. All but 11 patients fell within an age range of 20-59 yr, with a mean age of 38 yr. Fifty-one per cent were married or living with a partner, 37% were single and 13 % were separated, divorced or widowed. Illness

onset

When asked how long they had been ill, some patients cited two intervals, one associated with the initial development of symptoms and the other with a significant worsening in symptoms; in such cases, the longer interval was that taken. The mean duration of illness was 63 months; 46 % of the sample had been ill from 2 to 5 yr; 19% had been ill for less than 2 yr; 35% had been ill for 6 yr or more. Given the long periods of illness reported in some cases, patients’ descriptions of its onset should be treated with caution. With this caveat, 58% said that it had developed gradually over several months, and 42% that the onset had been sudden. The beginning of the illness was associated with an infection by the majority (63% responding ‘yes’ and 32% ‘possibly’) and, similarly, with preceding stress (54% ‘yes’ and 30% ‘possibly’). Perceived

current

illness severity

For most the illness continued to have a disabling effect; 82% of the sample said that they could now do only half, or less than half, of what they could do before its onset. However, 55% felt that they were improving in the long term, and only a minority (11%) felt that their illness was becoming worse. Symptoms were continuous

246

c.

RAY

et al.

for some but were more commonly intermittent; 31% were experiencing symptoms all of the time, 46% most of the time, and 23% some of the time. Patients answered a number of questions about variations in the severity of their symptoms. They were asked to choose from five responses ranging from definitely true to definitely untrue, with one of the options being ‘cannot say’. The percentages given here are for patients responding definitely or generally true. Many felt well or greatly better for days at a time (72%), while relatively few felt well or greatly better for weeks at a time (28 %). The majority reported that fatigue was exacerbated by slight physical effort or mental effort (87 and 83% respectively). In most cases this onset or exacerbation would normally be within 3 hr (63%), with only 6% claiming that it would be delayed by more than 24 hr. If brought on by effort, symptoms would typically last for several days or more for 58% of the sample. Perceptions

of cause and outcome

Very few patients saw their illness as having wholly or mainly a psychological cause (3 %), while more thought that the cause was wholly physical (2 1 X) or mainly physical (33%); 43% said that they believed it to be caused by both physical and psychological factors. There was some optimism about the outcome of the illness. Sixty per cent were optimistic or very optimistic compared with 20% who were pessimistic or very pessimistic (20% were unable to give an opinion). Patients with a shorter duration of illness, and those who felt that their condition was improving, were more likely to express such optimism (Kendall’s T = -0.20 and 0.52 respectively, both significant at p < 0.001). Factor analysis

of symptoms

Patients rated the extent to which they had experienced particular symptoms in the past month on a scale ranging from 0 to 4. This list comprised 96 items, and the data were factor analysed (using SPSS-X) to determine a reduced set of dimensions summarizing the specific items. The normality of the data was within reasonable limits for this purpose [ 401: there were only five items whose values for skewness exceeded + or - 1 .O. The method used was principal components analysis, which inserts unities in the diagonals to represent the communality of the items. There are several ways of determining the number of factors that should be extracted. One is to take all those factors with eigenvalues greater than one; however, this can lead to overfactoring with sample data and the number of factors increases with the number of variables [41] . A second method is to apply the ‘scree test’ [42], stopping at the last factor not on the scree and below which the differences in the eigenvalues associated with successive factors become substantially smaller [ 43 ] . The latter method indicated that four factors should be extracted, accounting for 47.3 % of the variance (this percentage is comparable with that explained by solutions for symptom data that have been reported in other contexts: [44-461). The four factors were then rotated to enhance their interpretability, using an orthogonal varimax rotation (with convergence achieved in seven iterations). This resulted in loadings which were very similar to those obtained with an oblique rotation. Examples of items contributing to each factor are listed in Tables I to IV.* The *The full list of symptoms and related data are available from the first author. items in the tables has been abbreviated for conciseness of presentation.

The wording

of the

Symptom TABLE

I.-EMOTIONAL

components

DISTRESS.

WITH

THE

MEANS

HIGHEST

241

in CFS (SD

FACTOR

IN

BRACKETS)

FOR ITEMS

LOADINGS

Loading Depressed Anxious Sad Tense Worthless Feelings of resentment Irritable Other people annoying you Impatient Worrying about things that do not matter Pessimistic about the future Rapid changes of mood Orthogonal

TABLE

rotation.

II.-FATIGUE.

Variance

MEANS HIGHEST

0.78 0.77 0.77 0.76 0.74 0.74 0.72 0.70 0.69 0.68 0.67 0.67

accounted

(SD

IN

FACTOR

BRACKETS)

FOR ITEMS

TABLE

III.-SOMATIC

Variance

accounted

SYMPTOMS. THE

MEANS

HIGHEST

0.81 0.78 0.78 0.74 0.74 0.13 0.71 0.71 0.69 0.66 0.66 0.64

Variance

(SD

FACTOR

accounted

Mean 3.08 2.68 2.85 2.60 2.70 2.48 2.52 3.00 2.40 2.68 2.67 2.40

(1.00) (1.23) (1.04) (1.16) (1.26) (1.27) (1.28) (1.02) (1.17) (1.22) (1.20) (1.33)

IN

BRACKETS)

FOR ITEMS

WITH

LOADINGS

Loading

rotation.

THE

for = 11.5%

Chilled or shivery Difficulty balancing Dizziness or giddiness Hot or cold spells Feeling like you have a temperature Numbness in some part of the body Blurred vision Breathlessness Muscles tender to the touch Stomach pain Sore throat Feeling faint Orthogonal

WITH

LOADINGS

Loading

rotation.

(1.22) (1.26) (1.31) (1.22) (1.44) (1.33) (1.17) (1.18) (1.18) (1.40) (1.36) (1.31)

for = 14.5%

Physically drained Slightest exercise makes you physically tired Physically tired when taking things easy Not having the physical energy to do anything Muscles weak after slight exercise Muscles weak after resting Muscles ache after slight exercise Physically tired after a good night’s sleep Limbs feeling heavy Having to stop doing something because of tiredness Difficulty standing for long Muscles ache after resting Orthogonal

Mean 1.96 2.08 2.02 2.24 1.43 1.54 2.18 1.91 2.10 1.82 1.76 2.04

0.62 0.61 0.58 0.57 0.55 0.53 0.52 0.51 0.51 0.50 0.50 0.48 for = 11 .O%

Mean 1.97 1.37 1.57 2.03 1.63 1.10 1.24 1.28 1.71 2.00 1.63 1.13

(1.32) (1.25) (1.27) (1.36) (1.38) (1.28j (1.25) (1.23) (1.38) (1.27) (1.42) (1.19)

C. RAY et al.

248

TABLE IV.-COGNITIVE DIFFICULTY. MEANS (SD IN BRACKETS) FOR ITEMS WITH THE HIGHEST FACTOR LOADINGS Loading Difficulty remembering things Slowness of thought Absent-mindedness Confusion Difficulty reasoning things out Forgetting what you are trying to say Difficulty finding the right word Difficulty following things Difficulty concentrating Difficulty understanding Brain feeling like cotton wool Slow to react Orthogonal

rotation.

Variance

0.75 0.73 0.72 0.72 0.70 0.67 0.66 0.65 0.64 0.64 0.63 0.59

accounted

Mean 2.45 2.18 2.17 2.10 2.02 2.22 2.32 1.43 2.41 1.74 2.11 1.70

(1.19) (1.23) (1.25) (1.38) (1.31)

(1.28) (1.23) (1.27) (1.17) (1.29) (1.45) (1.25)

for = 10.3 %

content of the factors was interpreted by examining items with loadings of 0.45 or above; such loadings are regarded as ‘fair’ [47] . The first factor contained items relating to feelings of depression, anxiety and anger (Table I), and was labelled Emotional Distress. The second factor was interpreted at Fatigue; items with the highest loadings were concerned with physical tiredness and muscular weakness and aching (Table II). However, four items not included in the table, but with loadings of 0.45 or above, referred to general mental fatigue (two of these were complex variables with significant loadings also on the fourth factor). The third factor comprised miscellaneous somatic symptoms suggestive of autonomic disturbance (Table III), and was labelled Somatic Symptoms. The fourth factor, termed Cognitive Difficulty, had significant loadings for items reflecting problems with memory, speed of thought, concentration and comprehension (Table IV). When the factors were obliquely rather than orthogonally rotated, the loadings of the items obtained were broadly similar, and the interpretation of the factors was unchanged. The next step in the data analysis was to derive factor scores, representing weighted combinations of the original items, and to correlate these with patients’ global reports of the illness. Noteworthy correlations emerged when the factors were rotated obliquely (Table V). However, an orthogonal rotation has advantages if factor scores are to be used as variables in subsequent analyses [40] , and this was thus adopted as the method of choice. An orthogonal rotation results in factors which delineate statistically independent variation, and such component scores are uncorrelated.

TABLE

V.-CORRELATIONS

BETWEEN

ED ED F ss ED = Emotional Distress; CD = Cognitive Difficulty.

THE FACTORS (OBLIQUE ROTATION)

F

SS

CD

0.34

0.39 0.41

0.40 0.42 0.38

F = Fatigue;

SS = Somatic

Symptoms;

Symptom

Factor scores and perceived

components

249

in CFS

illness severity

The factor scores were correlated with the items listed in Table VI. These items were selected from the questionnaire as being most relevant to perceptions of severity (the questions in full are presented in the appendix). Additionally, two items relating to perceptions of cause and outcome were also included in the analysis. Correlations are based upon an N of 170, excluding subjects with missing symptom data for whom factor scores were not obtained: there were no differences between missing and non-missing cases on the questionnaire items. The results for both Kendall’s tau and Spearman’s rho are presented, corrected for ties; T and rS are not numerically comparable, but both have the same power to detect association [48] . The levels of significance produced by these statistics coincided, thus enhancing confidence in the inferences made. Two-tailed tests were employed, since directional predictions could not be made consistently for all variables. TABLE

VI.-CORRELATIONS BETWEEN SYMPTOM FACTORS (ORTHOGONAL ROTATION) AND PERCEIVED ILLNESS SEVERITY. N= 170

ED Disability

-0.02 -0.03

course of the illness-t

-0.05 -0.06

Relative severity of illness in the past month Frequency

of symptoms

0.10 0.14 -0.06 -0.08

F

SS

CD

0.37** 0.48**

0.16* 0.21*

0.23** 0.30**

-0.33** -0.42**

-0.19* -0.24*

-0.19* -0.24*

0.34** 0.45**

0.26** 0.35**

0.10 0.14

0.46** 0.57**

0.23** 0.30**

0.12 0.15

Feeling better at a time

for days

0.06 0.07

-0.15 -0.19

-0.13 -0.16

-0.13 -0.18

Feeling better at a time

for weeks

0.01 0.01

-0.24** -0.30**

-0.13 -0.17

-0.20* -0.26*

Physical Mental

fatigability fatigability

-0.09 -0.11 0.04 0.06

0.33** 0.42**

0.17* 0.21*

0.16* 0.21*

0.14 0.18

0.18* 0.23*

0.34** 0.43**

ED = Emotional Distress; F = Fatigue; SS = Somatic Cognitive Difficulty. * p < 0.01 ** p < 0.001 (significance tests are two-tailed). Kendalls’ tau (upper line). Spearman’s rho (lower line). t Improvement positively scored.

Symptoms;

CD =

The Fatigue factor was positively related to level of disability and relative severity of symptoms in the past month, and negatively related to perceived improvement in the course of the illness. Patients with high scores on this factor were more likely to report a high frequency of symptoms and less likely to feel relatively better for weeks at a time. They were more prone to physical fatigability, but not to mental fatigability. High levels of Somatic Symptoms were associated with the relative severity of symptoms in the past month and with frequency of symptoms; Cognitive Difficulty was related to the level of disability reported and mental fatigability. In

250

C. RAY et al.

addition, the latter factors correlated with several other indices with a probability of < 0.01 (these correlations should be interpreted with caution because of the number of relationships examined). The Emotional Distress factor was not related to any of these aspects of the illness. However, with high scores, patients were somewhat more likely to see their illness as having a psychological contribution (T = 0.16, p < O.Ol), whereas patients with high Fatigue scores were more likely to attribute their illness to a physical cause (T = -0.17, p < 0.01). High symptom scores were negatively related to optimism about the illness’ outcome (Emotional Distress T = -0.28, p < 0.001; Fatigue T = -0.19, p < 0.01; Somatic Symptoms T= -0.16, p < 0.01). DISCUSSION

The factor analysis of symptoms yielded four conceptually distinct dimensions. The emotional distress factor was defined by subjective feelings of depression, anxiety and anger while somatic symptoms loaded on a different factor. This separation relates to a general issue concerning the assessment of affective disturbance in physical illness. Somatic symptoms are commonly included in measures of anxiety and depression, but they have an ambiguous status in physical illness where they may feature independently of emotional status [49-521. In a disorder such as CFS, whose aetiology has not yet been established, it is thus advisable to avoid confounding these dimensions, Several authors have pointed to the difficulty of assessing subjective fatigue and the need for reliable measures [53, 16, 37, 211. The composition of the fatigue factor was of interest in this context, comprising as it did items relating to muscular symptoms as well as to general physical fatigue. It was also of interest that specific cognitive difficulties loaded on a separate factor. Wessely and Powell [27] included such items in their assessment of ‘mental fatigue’ and found, as in this study, that these and physical fatigue items were associated with distinct factors. Overall, the analysis provided support for the utility of a dimensional approach to assessing symptoms in CFS. Through adopting an orthogonal rotation, the derived factor scores were themselves uncorrelated. Thus emotional distress could be assessed independently of other dimensions and, conversely, fatigue and other symptoms could be assessed independently of affect. Using these scores, the three dimensions of fatigue, somatic symptoms and cognitive difficulty were each found to be significantly associated with a number of indices of perceived illness severity, but there were no significant relationships between these indices and emotional distress. This suggests that the conclusion that affect plays an important role in the perception of illness severity [38] should be qualified. In the latter study, patients were assessed as part of a double-blind placebo-controlled evaluation of acyclovir therapy, and a rating of ‘wellness’ was found to correlate significantly with all dimensions of the Profile of Mood States, including anxiety, depression and anger. The present study prompts the rather different conclusion that affect per se does not play a pivotal role in the perceived severity of the ongoing illness. in that it is primarily fatigue and, to a lesser extent, somatic symptoms and cognitive difficulties that predict the latter. Nevertheless, affect may contribute indirectly to the perception of illness severity, to the extent that it correlates with these other symptom dimensions (Fig. 1).

Symptom components in CFS

b

fatigue other

and

_

4

symptoms

251

illness severity

FIG.

1.

These findings bear out the view generally expressed by patients that mood disturbance is not a feature of the illness with a similar status to fatigue and other symptoms. Outcomes tend to be attributed to factors with which they covary [ 541 , and a lack of independent relationship between emotional states and perceived severity could be one subjective basis on which patients de-emphasize their pertinence and attribute the illness primarily to physical rather than psychological causes. The appropriateness of this attribution remains open to debate [55] The syndrome could arguably represent a form of somatization [56, 571. On the other hand, these data would equally fit an organic disorder with associated emotional features; the functional status of emotions remains ambiguous in a number of chronic, medical conditions 158, 591 , and their salience in CFS should not be taken to imply that the syndrome is necessarily psychologically-driven. Though emotional distress was not independently associated with perceived illness severity, correlations with symptoms which did predict this were evident when the factors were obliquely rotated. Negative affect is commonly found to correlate with fatigue and with somatic and cognitive disturbance; causal relationships are more difficult to establish, particularly in the absence of a psychiatric diagnosis. Focusing on subjective health-related complaints, these overlap with negative affect in general adult and student samples [60-621 ; this commonality can be accounted for in different ways, with negative affect being regarded either as a reaction to discomfort and disability or, alternatively, as a factor which exacerbates health complaints. Persson and Sjoberg [63] concluded that the primary direction of influence is that of somatic experiences on mood, on the basis of a time series analysis of mood and physical symptoms in a small sample of healthy subjects. However, the hypothesis that negative affect is a reaction to health complaints has been challenged, given that emotional disturbance is not consistently found in the chronically ill [ 64, 651 . A key factor determining the emotional impact of chronic illness may be the nature of the symptoms or impairments which it involves. Within the general population, certain kinds of symptoms seem to be more clearly related to affect than others; diffuse symptoms such as weakness and fatigue have relatively high correlations with negative affect, while musculoskeletal symptoms are not as closely related [60, 631. Cognitive difficulties as such were not examined in these studies; the nature of their relationship with affect in CFS is ambiguous [66] , but it has been suggested that the impaired cognition reported by patients with CFS is a particularly debilitating

252

C. RAY et al.

and disturbing feature of their condition [ 671 . Thus, if comparisons are made between CFS and other illness groups, the nature of the latter will be important in determining the conclusions that can be drawn about emotional disturbance as a response to symptoms and impairment. CFS patients have higher rates of depression than patients with peripheral neuromuscular fatiguing illnesses [27, 681 . However, neuromuscular patients experience somewhat less physical fatigue, and they have markedly fewer cognitive difficulties and somatic symptoms [27] . It would be interesting to compare CFS with a range of illnesses which differ in their symptom profiles with regard to such dimensions, and to examine the relationship between these profiles and affect. Patients’ comments in the present study, though potentially biased by personal models of the illness, suggested the possibility of a reciprocal influence between mood and other symptoms (Fig. 1). Many claimed that discomfort in itself lowers mood. In addition, some emphasized in particular the debilitating nature of their symptoms and the effect that this has on their ability to cope with practical and emotional challenges. To summarize this theme, loss of energy, malaise and cognitive impairment reduce the ability to exercise control over events, with the result that negative outcomes are more likely to be experienced; in parallel, these symptoms enhance emotional vulnerability to such outcomes. Even everyday stressors can then have a disproportionate impact on mood. * Furthermore, the capacity to adapt to the life-style changes and frustrations imposed by illness will be influenced by coping behaviour [ 691; debility, to the extent that it impedes effective coping, may undermine such adaptation. Conversely, some patients also said that stress and negative emotions can exacerbate their symptoms, but without regarding the former as being causally sufficient. Responses to the questionnaire item asking about perceptions of cause are relevant here. The vast majority rejected the idea that psychological factors are wholly or mainly responsible for the illness; however, a significant proportion saw it as being caused by psychological as well as physical factors, a higher proportion in this sample than has been reported elsewhere [ 271 . A possible explanation for this perceived influence is that negative emotions modify symptom perception: a recent study induced negative mood in subjects experiencing symptoms of cold or flu, and found that this increased reporting of aches, pains and discomfort [ 711. Another possibility is that psychological distress triggers or enhances pathological processes that characterise CFS, for example, immune system dysregulation, as has been proposed in relation to multiple sclerosis [ 721 . Returning to the lack of association observed in this study between emotional distress and indices of perceived illness severity, several methodological factors should be considered. First, it is possible that more robust and sensitive measures of severity/disability would have elicited some relationship (there is a need for such measures appropriate to CFS); however, correlations for the other symptom components would then also be expected to increase in magnitude so that the disparity between components would remain. Second, patients could have selectively underreported affective symptoms; if this were the case, correlations with other variables would then be suppressed. Third, though the number of non-respondents was *It has, similarly, been suggested stressful events [ 701

that pain may make patients

more vulnerable

to non-illness

related

Symptom components in CFS

253

proportionally low, they may have differed in some significant respect from the group for whom data were available. More generally, the conclusions that can be drawn from this study are limited by its cross-sectional nature. Further information would be gained from a design which allowed correlations among symptom components to be assessed within as well as between subjects [73] . With a longitudinal design, the temporal relationship between changes on these different dimensions could also be charted. Such a study would offer clearer pointers to causal relationships within the ongoing illness. AcknoM,Iedgemenfs-This

work

was supported

by the Sir Jules Thorne

Charitable

Trust.

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APPENDIX

Disability How (a) (b) (c) (d) (e) Course

much I can I can I can I can I can

does your illness now affect your everyday life? hardly to anything compared with before. do about a quarter of what I could do before. do about half what I could do before. do about three quarters of what I could do before do most of what I could do before.

of the illness

Ignoring ‘ups and downs’, is your illness (a) getting better (b) getting neither better (c) getting worse?

Relative

severity

of illness

nor worse

in the past month

Has the past month been a good or bad one for you in terms of your (a) a very bad one (b) quite a bad one (c) neither good nor bad (d) quite a good one (e) a very good one

Frequency

of symptoms

Do you now have symptoms (a) all of the time (b) most of the time (c) some (d) rarely?

of the time

illness?

C. RAY et al.

256 Feeling

better for days at n time

Can you feel well, or greatly better, for days at a time? (a) definitely true (b) generally true (c) cannot say (d) generally untrue (e) definitely untrue

Feeling

better for weeks at a time

Can you feel well, or greatly better, for weeks or more at a time? (a) definitely true (b) generally true (c) cannot say (d) generally untrue (e) definitely untrue

Physical fat&ability Is your fatigue brought on or made worse by slight physical exercise? (a) definitely (d) generally

Mentd

true (b) generally true (c) cannot say untrue (e) definitely untrue

fatigability

Is your fatigue brought on or made worse by mental effort? (a) definitely (d) generally

true (b) generally true (c) cannot say untrue (e) definitely untrue