[Placebo effect: a contribution of social psychology]

This article reviews the psychosocial variables, which are of interest in the relationship between the patient and the physician. According to a classical model of social psychology, such a relationship might contribute to the placebo/nocebo effects. We develop herein various relational and contextual variables, taking into account four dimensions (intra-individual, interpersonal, positional and ideological) and their potential effects on therapeutic responses. This applies both in the setting of daily clinical practice and of clinical trials. The placebo effect offers an opportunity for collaboration and dialogue between social scientists and physicians.