Cognitive functioning in people with chronic fatigue syndrome: a comparison between subjective and objective measures.

OBJECTIVE: The purpose of this study was to examine the relationship between subjective and objective assessments of memory and attention in people with chronic fatigue syndrome (CFS), using tests that have previously detected deficits in CFS samples and measures of potential confounds. METHOD: Fifty people with CFS and 50 healthy controls were compared on subjective (memory and attention symptom severity, Cognitive Failures Questionnaire, Everyday Attention Questionnaires) and objective (California Verbal Learning Test, Rey-Osterreith Complex Figure Test, Paced Auditory Serial Addition Test, Stroop task) measures of memory and attention. Fatigue, sleep, depression, and anxiety were also assessed. RESULTS: The CFS group reported experiencing more cognitive problems than the controls, but the two groups did not differ on the cognitive tests. Scores on the subjective and objective measures were not correlated in either group. Depression was positively correlated with increased severity of cognitive problems in both the CFS and control groups. CONCLUSIONS: There is little evidence for a relationship between subjective and objective measures of cognitive functioning for both people with CFS and healthy controls, which suggests that they may be capturing different constructs. Problems with memory and attention in everyday life are a significant part of CFS. Depression appears to be related to subjective problems but does not fully explain them.

Cognitive deficits in chronic fatigue syndrome and their relationship to psychological status, symptomatology, and everyday functioning.

OBJECTIVE: To examine cognitive deficits in people with chronic fatigue syndrome (CFS) and their relationship to psychological status, CFS symptoms, and everyday functioning. METHOD: The current study compared the cognitive performance (reaction time, attention, memory, motor functioning, verbal abilities, and visuospatial abilities) of a sample with CFS (n = 50) with that of a sample of healthy controls (n = 50), all of whom had demonstrated high levels of effort and an intention to perform well, and examined the extent to which psychological status, CFS symptoms, and everyday functioning were related to cognitive performance. RESULTS: The CFS group showed impaired information processing speed (reaction time), relative to the controls, but comparable performance on tests of attention, memory, motor functioning, verbal ability, and visuospatial ability. Moreover, information processing speed was not related to psychiatric status, depression, anxiety, the number or severity of CFS symptoms, fatigue, sleep quality, or everyday functioning. CONCLUSION: A slowing in information processing speed appears to be the main cognitive deficit seen in persons with CFS whose performance on effort tests is not compromised. Importantly, this slowing does not appear to be the consequence of other CFS-related variables, such as depression and fatigue, or motor speed.

Test effort in persons with Chronic Fatigue Syndrome when assessed using the Validity Indicator Profile.

The current study examined the potential contribution of suboptimal effort to the cognitive deficits that are associated with Chronic Fatigue Syndrome (CFS) using the Validity Indicator Profile (VIP). Unlike most tests of effort, the VIP distinguishes between intentional and unintentional poor performance and does not assess cognitive functions that are affected by CFS, thereby reducing the risk of mistakenly attributing genuinely poor performance to reduced effort. The VIP was administered to 54 persons with CFS and 54 matched healthy community controls, and performance categorized into 1 of 4 response styles (valid: compliant; invalid: suppressed, irrelevant, inconsistent), based on the level of effort expended (high or low) and the intention to perform well or not. VIP performance was classified as valid for the majority of participants (CFS and controls), indicating high levels of effort and an intention to perform well. Three participants in the CFS group and four in the control group showed low levels of effort but an intention to do well (invalid: inconsistent). No participant performed in a manner indicative of an intent to perform poorly (invalid: suppressed, inconsistent). These findings suggest that poor effort is unlikely to contribute to cognitive test performance of persons with CFS.