Fatigue and psychiatric illness in a large community sample of persons with multiple sclerosis.

BACKGROUND: Fatigue and depression are among the most common and disabling symptoms in multiple sclerosis (MS), but the nature and extent of the relationships between fatigue and psychiatric disorders in MS patients remain poorly understood.
METHODS: A mail survey was completed by 739 members of the King County (WA) MS Association. Fatigue was evaluated by questions from the Modified Fatigue Impact Scale (MFIS), depressive symptoms by the Center for Epidemiologic Studies Depression Scale (CES-D), substance-use disorders from the PRIME-MD. Information on demographics, employment and characteristics of MS was also collected. Logistic regression was used to identify covariates significantly associated with disabling fatigue. Receiver operating characteristic (ROC) curve analysis evaluated the sensitivity and specificity of fatigue for depression.
RESULTS: Twenty-five percent of this community-dwelling sample reported that their activities were often or almost always limited by fatigue. Seventy-six percent of subjects with disabling fatigue had significant depressive symptoms (CES-D >16), compared with 31% of those without disabling fatigue. Depression was strongly associated with fatigue, after controlling for age, gender, marital status, and severity, course and duration of illness. In logistic regression analysis, subjects with clinically significant depressive symptoms (CES-D >16) were much more likely to report disabling fatigue: OR = 6.24 (4.16, 9.35). Anxiety and substance-use disorders did not have the same strong associations with fatigue. Fatigue was highly sensitive and specific for clinically significant depressive symptoms.
CONCLUSIONS: Disabling fatigue is strongly associated with clinically significant depressive symptoms. Patients who report disabling fatigue should be screened for depression.