title: A twin study of cognitive function in chronic fatigue syndrome: the effects of sudden illness onset.
abstract: Variable reports of neuropsychological deficits in individuals with chronic fatigue syndrome (CFS) may, in part, be attributable to methodological limitations. In this study, these limitations were addressed by controlling for genetic and environmental influences and by assessing the effects of comorbid depression and mode of illness onset. Specifically, the researchers conducted a co-twin control study of 22 pairs of monozygotic twins, in which 1 twin met strict criteria for CFS and the co-twin was healthy. Twins underwent a structured psychiatric interview and comprehensive neuropsychological assessment evaluating 6 cognitive domains. Results indicated that twin groups had similar intellectual and visual memory functioning, but fatigued twins exhibited decreases in motor functions (p = .05), speed of information processing (p = .02), verbal memory (p = .02), and executive functioning (p = .01). Major depression did not affect neuropsychological functioning among fatigued twins, although twins with sudden illness onset demonstrated slowed information processing compared with those with gradual onset (p = .01). Sudden onset CFS was associated with reduced speed of information processing. If confirmed, these findings suggest the need to distinguish illness onset in future CFS studies and may have implications for treatment, cognitive rehabilitation, and disability determination.
authors.affiliation: Department of Psychology, University of Hawaii, Honolulu, HI, USA.
authors.forename: Keith H
authors.initials: KH
authors.lastname: Claypoole
authors.forename: Carolyn
authors.initials: C
authors.lastname: Noonan
authors.forename: Roderick K
authors.initials: RK
authors.lastname: Mahurin
authors.forename: Jack
authors.initials: J
authors.lastname: Goldberg
authors.forename: Tom
authors.initials: T
authors.lastname: Erickson
authors.forename: Dedra
authors.initials: D
authors.lastname: Buchwald
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology; D003071:Cognition / Q000502:physiology*; D003865:Major Depressive Disorder / Q000150:complications / Q000523:psychology; D015673:Fatigue Syndrome, Chronic / Q000523:psychology*; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology; D008606:Mental Processes / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D021641:Recognition, Psychology / Q000502:physiology; D014430:Twins, Monozygotic; D014706:Verbal Learning / Q000502:physiology; D014888:Wechsler Scales