Cognitive deficits in patients with chronic fatigue syndrome compared to those with major depressive disorder and healthy controls

Object: It is frequently reported that cognitive complaints accompany the chronic fatigue syndrome (CFS). However, studies on cognition in CFS have yielded conflicting results. The neuropsychological literature on this subject is plagued by methodological difficulties, including, for example, the existence of comorbid depression, which is also associated with cognitive impairments.
Patients and Methods: Twenty-five patients with CFS, 25 patients with major depressive disorder (MDD), and 25 healthy control subjects were given standardized tests of attention, working memory, and verbal and visual episodic memory, and were also tested for effects related to lack of effort/simulation, suggestibility, and fatigue.
Results: Patients with CFS had slower phasic alertness, and also had impaired working, visual and verbal episodic memory compared to controls. They were, however, no more sensitive than the other groups to suggestibility or to fatigue induced during the cognitive session. Cognitive impairments in MDD patients were strongly associated with depression and subjective fatigue; in patients with CFS, there was a weaker correlation between cognition and depression (and no correlation with fatigue).
Conclusions: This study confirms the presence of an objective impairment in attention and memory in patients with CFS but with good mobilization of effort and without exaggerated suggestibility.