L’effet placebo : généralités et spécificités en psychiatrie (dépression et schizophrénie)

Abstract

Placebos, consequences of their use, the placebo effect and the associated negative effects, the nocebo effect, have been widely studied. However, the lack of any consensus definition makes the interpretation and analysis of such findings difficult. In this article, we will review existing definitions and factors affecting the placebo effect in medicine. We will then consider the possible mechanisms of action of the placebo effect, with a view to improving understanding of this issue. Finally, we will analyse data relating to placebos used in psychiatry and, more specifically, for schizophrenic patients. In an extensive review of the literature, we identified the various factors playing a role in the appearance of placebo effects in general medicine. As well as purely factual elements, such as the disorder, the sex of the subject and the treatment given, the placebo effect is strongly correlated with the quality of the relationship between the doctor and patient and with the capacity of the patient to communicate and establish a link. The attitude of the doctor, the temperament of the subject and the expectations and beliefs of each also contribute to the appearance and extent of a placebo effect. We then investigated placebo effects in psychiatry, particularly in depressed patients (the most widely studied condition) where studies have shown particular efficacy. We also addressed the use of placebos in schizophrenia: the placebo effect in patients with this disorder is essentially used as a tool for assessing new molecules to be released onto the market but the phenomenon itself has been little studied, if at all. Thus, it is of particular interest to consider in detail the use of placebos in schizophrenia, to try to gain a deeper understanding of the factors involved. This will allow potential specific effects associated with placebo use in this disorder to be established, improving the integration of placebos into therapy and to optimize the efficacy of treatment prescribed, taking into account mental state; indeed, the placebo effect is present in all treatments, whether involving a placebo or an active compound.