The concept of 'illness without disease' impedes understanding of chronic fatigue syndrome: a response to Sharpe and Greco.

In a recent article in , Sharpe and Greco characterise myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) as an 'illness without disease', citing the absence of identified diagnostic markers. They attribute patients' rejection of psychological and behavioural interventions, such as cognitive-behavioural therapy (CBT) and graded exercise therapy (GET), to a 'paradox' resulting from a supposed failure to acknowledge that 'there is no good objective evidence of bodily disease'. In response, we explain that understandings about the causes of and treatments for medical complaints have shifted across centuries, and that conditions once thought to be 'psychosomatic' have later been determined to have physiological causes. We also note that Sharpe and Greco do not disclose that leading scientists and physicians believe that ME/CFS is a biomedical disease, and that numerous experts, not just patients, have rejected the research underlying the CBT/GET treatment approach. In conclusion, we remind investigators that medical classifications are always subject to revision based on subsequent research, and we therefore call for more humility before declaring categorically that patients are experiencing 'illness without disease'.