Chronic fatigue syndrome is a complex illness that has no known cause or cure. Myriad symptoms include severe malaise, muscle and joint pain, sleep and mood disturbances and headache. The symptoms continue for at least six months and cannot be explained by any other medical conditions.

A recent analysis of 29 studies of those with CFS by Dr Hyong Jin Cho of King’s College London suggests that, contrary to conventional wisdom, CFS patients respond to placebos at a lower rate than people with many other illnesses. Only 19.6% of patients with CFS improved after receiving inactive treatments, compared with a widely accepted figure of about 30% for other conditions. Because the placebo effect seems to be strongest in diseases with highly subjective symptoms, some medical professionals had believed it could be as high as 50% among CFS patients.

The study also showed that the placebo response is 24% for medical interventions but only 14% for psychiatric/psychological treatments. The authors say the reason may be that many CFS sufferers seen in specialist settings or self-help groups ‘have a firm conviction that their illness is of physical origin’ and thus would have little faith in psychiatric/psychological treatments. This finding supports the idea that the placebo response is greatly influenced by patients’ expectations of improvement.

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First Published in August 2008

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