The neurobiological underpinnings of placebo and nocebo effects.

The placebo effect, once considered only a nuisance in clinical research, is today a target of scientific inquiry that allows us understand how words, rituals and, more in general, the whole psychosocial context around the patient, affect the response to a treatment and the course of a disease. Today we are in a good position to study all these complex psychological factors by using a physiological and neuroscientific approach that uses modern neurobiological tools to probe different brain functions. Since a placebo is represented by the whole ritual of the therapeutic act, the main concept that has emerged today is that words and rituals may modulate the same biochemical pathways that are modulated by drugs. Most of our knowledge about these mechanisms comes from the field of pain, and represents a biomedical, psychological and philosophical enterprise that is changing the way we approach and interpret medicine, psychology and human biology. If on the one hand we know some of the mechanisms of drug action in the central nervous system, on the other we can now understand how the clinician-patient interaction may affect different physiological functions. In fact, the placebo effect and the therapist-patient relationship can be approached by using the same biochemical, cellular and physiological tools of the materia medica. This represents an epochal transition, in which the distinction between drugs and words is progressively getting thinner, and which helps us overcome the old dichotomy between psychology and biology.