Neuropsychological correlates of chronic fatigue syndrome.
Neuropsychological deficits have been implicated in Chronic Fatigue Syndrome (CFS) and there is some indication that cerebral efficiency is compromised in these patients. To further investigate the nature of this impairment, 20 patients who had received a medical diagnosis of CFS were neuropsychologically assessed and compared with age-, sex-, and education-matched controls (20 depressed and 20 healthy subjects). The test battery consisted of the Grooved Pegboard Trail Making Test, Symbol Digit Modalities Test, Auditory-Verbal Learning Test, Visual Design Learning Test, Controlled Oral Word Association Test and Paced Auditory Serial Addition Task. Additional measures included a CFS symptom checklist, SCL-90-R and Cognitive Failures Questionnaire (CFQ). Univariate statistical analysis revealed a significant difference between CFS patients and healthy individuals on only one measure; the "S" trial of the COWAT (F[2,59]=3.30, p <.05). This finding suggests the existence of subtle but detectable neuropsychological difficulty in executive or attentional mechanisms in CFS patients. Further analysis revealed that the observed finding could not be attributed to depression or medication side-effects. Although a trend of declining neuropsychological test performance was evident in moving across the spectrum of healthy, depressed, and CFS samples, this reached significance only for the CFS/depressed versus healthy comparison X22  = 9.40, p < .05). The overall similarity of the neuropsychological profiles of CFS and depressed patients was noted, while an additional finding was the discrepancy between reported levels of subjective cognitive failure (CFQ) and objective neuropsychological findings in the CFS patients. The SCL-90-R profiles of the CFS and depressed patients were also found to be similar in terms of reported levels of psychological distress; however group discrimination was evident on two subscales (Somatization and Obsessive-Compulsive). Although the CFS and depressed controls did not differ with respect to levels of depression, there were some indications of a differential impact of depressive symptomatology on neuropsychological functioning. Taken together, the results of this study indicate that while subtle deficits are detectable in the neuropsychological profiles of CPS patients, the magnitude of impairment appears insufficient to significantly interfere with everyday cognitive functioning.