The paper by Christodoulou et al in this issue of the Journal (pp 431–4) draws attention to memory deficits in some patients with operationally defined chronic fatigue syndrome, and days of (enforced) physical inactivity. Many studies have assessed cognitive dysfunction in patients with chronic fatigue. The earliest reported superior abilities in such patients against controls or age matched normal subjects, probably reflecting a biased selection of cases from higher socioeconomic groups. Later studies have been the subject of at least two major reviews.1 2

Patients with chronic fatigue syndrome do not have clear evidence of either general intellectual decline, sensory deficits (assessed using evoked potentials), or perceptual impairments. Reaction times have, not surprisingly, been found to be slower. Deficits do emerge …