The placebo response in the treatment of chronic fatigue syndrome: a systematic review and meta-analysis.

The placebo response is conventionally asserted to be high in chronic fatigue syndrome (CFS) because of the latter's subjective nature and obscure pathogenesis, but no systematic review of placebo responses has been undertaken. We report such a study. Patient expectation is known to be important in the placebo response. It is also known that CFS patients attending specialist clinics often have strong physical attributions regarding causation and hence skepticism about psychological or psychiatric interventions. If so, the placebo response in CFS may be influenced by the type of intervention according to its perceived rationale. We aimed to estimate the summary placebo response in clinical trials of CFS and to determine whether intervention type influences the placebo response in CFS.