According to the new analysis by Dr. Hyong Jin Cho of King's College London and colleagues, 19.6 percent of patients with chronic fatigue syndrome improved after receiving inactive treatments, compared with a widely accepted figure of about 30 percent for other conditions.
Because the placebo effect seems to be strongest in diseases with highly subjective symptoms, some medical professionals believed it could be as high as 50 percent among CFS patients.
The review, reported in the current issue of Psychosomatic Medicine, pooled data from 29 studies in which 1,016 people with CFS received various placebos.
CFS 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. The Centers for Disease Control and Prevention estimate that as many as 500,000 Americans may have CFS or related conditions.
With so many mysteries surrounding CFS, a great deal of controversy exists among both doctors and patients as to whether its origins are primarily psychological or physiological. Current evidence suggests that emotional or social stresses such as bereavement or problems at work, combined with other triggers such as common viral infections, contribute to the disorder. Additional factors, such as avoidance of physical activity, may cause the symptoms to become chronic, says Cho.
The authors propose several possible explanations for the surprisingly low placebo response revealed in the analysis. Perhaps patients have low expectations due to the reality that CFS is very difficult to treat and often persists for many years. Alternatively
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Contact: Dr. Hyong Jin Cho
h.cho@cop.kcl.ac.uk
Center for the Advancement of Health
22-Mar-2005