Illness behaviour in the chronic fatigue syndrome and multiple sclerosis

Wood et al compared patients with the chronic fatigue syndrome with patients with various muscle diseases and found a threefold increase in psychiatric diagnoses in the group with the chronic fatigue syndrome. 2 Wessely et al describe an important prospective cohort study and conclude that common infections play little part in causing the chronic fatigue syndrome but that both previous psychological disorder and previous fatigue are associated with its development. 3 We agree with Trigwell and colleagues that illness behaviour is highly relevant to the chronic fatigue syndrome, but we share their reservations about the particular method of assessing this.