Toto je mimochodom dost efektivne spochybnovane. Je mozne ze placebo efekt neexistuje alebo je silno overrated. o.i.:
'The placebo effect' has become a catchall term for a positive change in health not attributable to medication or treatment. (...) the change can be due to many things, such as regression: spontaneous improvement, fluctuation of symptoms, regression to the mean, additional treatment, conditional switching of placebo treatment, scaling bias, irrelevant response variables, answers of politeness, experimental subordination, conditioned answers, neurotic or psychotic misjudgment, psychosomatic phenomena, misquotation.
...
In May 2001, The New England Journal of Medicine published an article that called into question the validity of the placebo effect. "Is the Placebo Powerless? An Analysis of Clinical Trials Comparing Placebo with No Treatment" by Danish researchers Asbjørn Hróbjartsson and Peter C. Götzsche "found little evidence in general that placebos had powerful clinical effects." Their meta-analysis of 114 studies found that "compared with no treatment, placebo had no significant effect on binary outcomes, regardless of whether these outcomes were subjective or objective. For the trials with continuous outcomes, placebo had a beneficial effect, but the effect decreased with increasing sample size, indicating a possible bias related to the effects of small trials."

"The high levels of placebo effect which have been repeatedly reported in many articles, in our mind are the result of flawed research methodology," said Dr. Hróbjartsson, professor of medical philosophy and research methodology at the University of Copenhagen.
http://www.skepdic.com/placebo.html