Open versus hidden medical treatments: the patient's knowledge about a therapy affects the therapy outcome.

Any medical treatment has 2 components, the first being the specific effects of the treatment itself, the second, the knowledge that the treatment is being performed (the placebo effect). So far, the placebo effect has been studied by eliminating the specific effects of the therapy through the administration of a dummy treatment. In this study, the authors reversed this experimental approach. In fact, whereas the specific effects of the treatment were maintained constant, the patient's knowledge that the therapy was being performed was done away with. To do this, the authors performed hidden medical treatments and compared these with the open ones. The results show that the hidden administrations of pharmacological and nonpharmacological therapies are less effective than the open ones.