THE PERSISTENCE OF FATIGUE IN CHRONIC-FATIGUE-SYNDROME AND MULTIPLE-SCLEROSIS - DEVELOPMENT OF A MODEL

The cause of chronic fatigue syndrome (CFS) is unknown. With respect t o factors perpetuating fatigue, on the other hand, a model has been po stulated in the literature in which behavioral, cognitive, and affecti ve factors play a role in perpetuating fatigue. In the present study, this hypothesized model was tested on patients with CFS and on fatigue d patients with multiple sclerosis (MS). The model was formulated in t erms of cause-and-effect relationships and an integral test of this mo del was performed by the statistical technique, ''structural equation modeling,'' in 51 patients with chronic fatigue syndrome and 50 patien ts with multiple sclerosis matched for age, gender, and education. Att ributing complaints to a somatic cause produced low levels of physical activity, which in turn had a causal effect on fatigue severity. Depr ession had to be deleted from the model. Sense of control over symptom s and focusing on bodily symptoms each had a direct causal effect on f atigue. The model showed an excellent fit for CFS patients, but was re jected for MS patients. Therefore, a new model for MS patients had to be developed in which sense of control had a causal effect on fatigue. In the MS model, no causal relationship was found between the physica l state as measured by the Expanded Disability Status Score (EDSS) and fatigue or functional impairment. The present study shows that cognit ive and behavioral factors are involved in the persistence of fatigue. Treatment should be directed at these factors. The processes involved in the subjective experience of fatigue in CFS were different from th e processes related to fatigue in MS. (C) 1998 Elsevier Science Inc.