Cognitive fatigue in patients with multiple sclerosis (PwMS) is not independently related to objective cognitive impairment, according to a recent study. Depression may influence cognitive function of PwMS, primarily when it is severe. Therefore, cognitive impairment in PwMS should not be ascribed to fatigue or mild depression. PwMS (n=699) completed a computerized cognitive testing battery with age- and education-adjusted cognitive domain scores. Disability (Expanded Disability Status Scale [EDSS]), cognitive fatigue, and depression were concurrently evaluated. Researchers found:

• Both cognitive fatigue and depression were significantly and negatively correlated with the same cognitive domains: information processing speed, executive function, attention, motor function, and memory.
• Multivariate analysis revealed significant, but small, independent correlations only between depression and neuropsychological test results, while cognitive fatigue had no independent correlation with objective cognitive function except for a trend toward impaired motor function in highly-fatigued PwMS.
• Depression and cognitive fatigue accounted for no more than 6% of the variance in objective cognitive domain scores.