[Placebo and the relationship between doctors and patients. Overview].

In medicine, placebos are used both in scientific studies and for practical therapeutic purposes. In evidence-based medicine, the efficacy of treatment may be determined as the difference between the effects of the verum (the active study drug) and the placebo, the latter being a substance lacking specific action on the disease under consideration. However, the improvements in patients' conditions under placebo treatment may be substantial and comparable to those with verum. Genuine placebos predominate in clinical studies, while pseudoplacebos prevail in practical therapy. The term pseudoplacebo can also be applied to many procedures in complementary medicine, including homeopathic medicine (Büchel et al., Placebo in der Medizin, 2011). The comprehensive definition of placebo, as used in a report by the German Medical Association (Büchel et al., Placebo in der Medizin, 2011), states that a placebo effect may occur even when treating with verum. The placebo effect is modulated by the context of the treatment, by the expectations of the patients and the doctors, and by the success of the relationship between doctors and patients. A number of unspecific effects, e.g., spontaneous alleviation, statistical effects, variance with time, methodological errors, in addition to the placebo effect make up the total response that is called"placebo reaction." A complete list of the effectiveness of placebo for all important diseases is still lacking. Further, it is not possible to predict which patients will respond to placebo. Which characteristics of doctors are important (competence, empathy, communicative ability and partnership, trust) in order to achieve a placebo effect, particularly in addition to the verum effect measures of evidence-based medicine? Are there doctors who are better in this than others? Could the nocebo effect weaken the efficacy of treatment in evidence-based medicine? Since a placebo effect may occur in almost any standard therapy, information about placebos should be provided during medical education and continuing medical education (CME). The use of placebo in clinical studies is ethically justified and lawful in consenting patients if there is no other effective treatment available with which the test substance could be compared. For daily practical therapeutic purposes, placebos may be ethically acceptable and lawful if there is no effective therapy available, if the complaints are minor, if the patient expressly wishes treatment, and if there is a reasonable likelihood of success. However, an explanation of the expected benefits and risks must be provided to the patients. At present, there are two explanatory theories for the mechanism of action of placebo, namely, the associative and the mentalistic explanation (Büchel et al., Placebo in der Medizin, 2011). Interestingly, effects of placebo and of verum can be localized in the brain by physiological and anatomical techniques. With many open questions remaining, research on placebo is currently very active. These aspect and neurobiological findings in particular may facilitate for "scientifically" educated doctors to accept that ineffective materials, i.e., placebos, are in fact effective.