Cognitive functioning in patients with chronic fatigue syndrome: Slowed information processing or a deficit in attentional selectivity?

Objective: By addressing numerous statistical, theoretical, and methodological weaknesses of existing research on chronic fatigue syndrome (CFS), this study attempted to examine closely whether cognitive dysfunction in CFS patients is restricted to slowed information processing or whether it extends to less efficient attentional selectivity.

Method: In an online study, 83 CFS patients and 83 healthy controls (all French-speaking volunteers) first completed the Multidimensional Chronic Asthenia Scale and then performed the two-to-one version of the Stroop task known to carefully measure different components of the Stroop effect including the targeted Stroop interference (i.e., prima facie indicators of attentional selectivity).

Results: Adequately powered analyses of raw reaction times pointed to differences in the magnitude of Stroop interference between CFS patients and healthy controls. However, these differences are entirely explained by generally slower processing speed in CFS patients. Indeed, no such differences were found when standardized (i.e., z scored) reaction times that take into account preexisting differences in processing speed were analyzed, and this absence of differences was attested-for the first time-by strong Bayesian evidence in favor of the null.

Conclusion: Although the present study showed that attentional selectivity is not impaired in CFS patients and that their cognitive dysfunction is restricted to slowed information processing, other studies are still needed to fully understand cognitive impairments associated with CFS. (PsycInfo Database Record (c) 2025 APA, all rights reserved).