Cognitive performance is of clinical importance, but is unrelated to pain severity in women with chronic fatigue syndrome.

Observed Findings

• Pain severity was not significantly associated with objective cognitive performance in either CFS patients or healthy controls.
• Fatigue measured by the CFS Symptom List (but not the CIS questionnaire) was significantly correlated with sustained attention deficits in CFS patients.
• Self-reported mental health was negatively correlated with all investigated cognitive domains (attention, processing speed, working memory) in the CFS group.
• Objective cognitive deficits were measurable in CFS patients using standardized performance tests.
• Cognitive impairment was not simply a reflection of pain severity, distinguishing CFS from typical chronic pain populations.

Inferred Conclusions

• Cognitive dysfunction in ME/CFS is clinically important and objectively measurable, independent of pain severity.
• Fatigue (measured as a state-like variable) is more strongly associated with cognitive deficits than trait-like fatigue measures, suggesting cognitive fatigue in ME/CFS may be fluctuating rather than stable.
• Pain in ME/CFS may have a unique underlying mechanism distinct from other chronic pain conditions, given its lack of association with cognitive performance.
• Mental health factors significantly correlate with cognitive performance in ME/CFS and warrant clinical attention.

Remaining Questions