Objective: To assess cognitive function in patients with chronic fatigue syndrome (CFS) and multiple sclerosis (MS) and to evaluate the role of depressive symptoms in cognitive performance. Design: Case-control. All subjects were given a neuropsychological battery, self-report measures of depression and fatigue, and a global cognitive impairment rating by a neuropsychologist ''blinded'' to clinical diagnosis. Patients with MS and CFS were additionally evaluated with a Structured Clinical Interview for DSM-III-R (Diagnostic ann Statistical Manual of Mental Disorders, Revised Third Edition) disorders. Setting: Institutional and private neurological practices and the community at large. Patients: Twenty patients with CFS diagnosed in accord with the Centers for Disease Control and Prevention-revised criteria who had cognitive complaints; 20 patients with clinically definite MS who were ambulatory and were matched for fatigue severity, age, and education to CFS subjects; and 20 age- and education-matched healthy controls. Results: Patients with CFS had significantly elevated depression symptoms compared with patients with MS and healthy controls (P<.001) and had a greater lifetime prevalence of depression and dysthymia compared with MS subjects. Patients with CFS, relative to controls, performed more poorly on the Digit Symbol subtest (P=.023) and showed a trend for poorer performance on logical memory (P=.087). Patients with MS compared with controls had more widespread differences of greater magnitude on the Digit Span (P<.004) and Digit Symbol (P<.001), Trail Making parts A (P=.022) and B (P=.037), and Controlled Oral Word Association (P=.043) tests. Patients with MS also showed a trend of poorer performance on the Booklet Category Test (P=.089). When patients with CFS and MS were directly compared, MS subjects had lower scores on all measures, but the differences reached significance only for the Digit Span measure of attention (P=.035). Conclusions: Patients with CFS compared with MS have more depressive symptoms but less cognitive impairment. Relative to controls, a subset of CFS subjects did poorly on tests of visuomotor search and on the logical memory measure of the Wechsler Memory Scale-revised. Poor performance of logical memory in CFS appears to be related to depression, while visuomotor deficits in CFS are unrelated. Cognitive deficits in patients with MS are more widespread compared with those in patients with CFS and are independent of depressive symptoms.
