Neurovegetative symptoms in patients with multiple sclerosis: fatigue, not depression

Elucidating the relationship between fatigue and depression in multiple sclerosis (MS) patients is complicated by ambiguity regarding how these two constructs should be delineated. Neurovegetative symptoms of depression may reflect depression in MS patients, as they do in non-neurological populations; instead these items may measure disease-related fatigue; or disease-related fatigue and depression may reflect the same syndrome in MS patients. The present study sought to evaluate these possibilities by characterizing the underlying factor structure of self-report items designed to measure fatigue and depression symptoms. Questionnaires designed to measure fatigue and depression were administered to 174 MS patients and 84 healthy controls, and these items were subject to factor analysis. Results suggest that neurovegetative symptoms are poor indicators of depression in MS patients. Neurovegetative depression items were removed from the final model due to poor psychometric properties, or they loaded on Fatigue or Sleep Disturbance factors. The correlation between latent factors Depression and Fatigue was large (.47), but does not indicate that these phenomena are manifestations of the same construct. Hence, the results of this study support the notion that vegetative symptoms of depression do not reflect depression in MS patients, but instead measure symptoms of fatigue and sleep disturbance.