Cochrane database Jan. 2010
Placebo effects are often claimed to substantially improve patient-reported and observer-reported outcomes across many clinical conditions, but most reports are from biased research without controls.
This Cochrane database systematic review looked at over 200 trials and discussed the effect and the findings. Many CAM practioners and adherents of alternative ‘medicine’ become, by default promoters of the value of placebo effects after such interventions. This is due to the increasing awareness that substantial, curative benefits from most CAM procedures are simply not forthcoming in well-done studies. Over the last several years Placebo effects have been relegated to the status of mundane… as opposed to miraculous.
The conclusions of this review suggest:
“Placebo interventions do not appear to have important clinical effects in general”. “In certain settings patient-reported outcomes of pain and nausea can be influenced. The effect on pain varies considerably and it’s difficult to distinguish it from biased reporting. Variations in placebo effect can be partly explained by how trials are conducted and how patients are informed”.