"Abnormal" illness behaviour in chronic fatigue syndrome and multiple sclerosis.

OBJECTIVE

To investigate the presence of abnormal illness behaviour in patients with a diagnosis of chronic fatigue syndrome.

DESIGN

A cross sectional descriptive study using the illness behaviour questionnaire to compare illness behaviour scores and illness behaviour profiles of patients with chronic fatigue syndrome and patients with multiple sclerosis.

SETTING

A multidisciplinary fatigue clinic and a teaching hospital neurology outpatient clinic.

SUBJECTS

98 patients satisfying the Oxford criteria for chronic fatigue syndrome and 78 patients with a diagnosis of multiple sclerosis.

MAIN OUTCOME MEASURE

Responses to the 62 item illness behaviour questionnaire.

RESULTS

90 (92%) patients in the chronic fatigue syndrome group and 70 (90%) in the multiple sclerosis group completed the illness behaviour questionnaire. Both groups had significantly high scores on the general hypochondriasis and disease conviction subscales and significantly low scores on the psychological versus somatic concern subscale, as measured in relation to normative data. There were, however, no significant differences in the subscale scores between the two groups and the two groups had identical illness behaviour profiles.

CONCLUSION

Scores on the illness behaviour questionnaire cannot be taken as evidence that chronic fatigue syndrome is a variety of abnormal illness behaviour, because the same profile occurs in multiple sclerosis. Neither can they be taken as evidence that chronic fatigue and multiple sclerosis share an aetiology. More needs to be known about the origins of illness beliefs in chronic fatigue syndrome, especially as they are important in determining outcome.