Nocebo and Pain

A placebo effect is the effect that follows the administration of a placebo, that is, of an inert pharmacological or physical treatment. It is important to point out that the inert treatment is given along with contextual stimuli, for example, verbal suggestions of clinical improvement that make the patient believe that the treatment is real and effective. Therefore, a placebo would be better defined as an inert treatment plus the context that tells the patient a therapeutic act is being performed. The nocebo effect is a phenomenon that is opposite to the placebo effect. To induce a nocebo effect, the inert substance is given along with a negative context, for example, verbal suggestions of clinical worsening, so as to induce negative expectations about the outcome. The term nocebo (“I shall harm”) was introduced in contrast to the term placebo (“I shall please”) by some authors to distinguish the pleasing from the noxious effects of placebos (Kennedy, 1961; Pogge, 1963; Kissel & Barrucand, 1964; Hahn, 1985, 1997). Therefore, if the positive psychosocial context, which is typical of the placebo effect, is reversed, the nocebo effect can be studied. To differentiate nocebo effects and placebo effects from spontaneous remission and other confounding factors, they are calculated as the symptom difference between a nocebotreated or placebo-treated group and a no-treatment group (Fields & Levine, 1984). From an ethical point of view, the investigation of the nocebo effect is difficult to carry out. In fact, whereas the induction of placebo responses is certainly ethical in many circumstances (Benedetti & Colloca, 2004), the induction of nocebo responses represents a stressful and anxiogenic procedure, because verbally induced negative expectations of symptom worsening may lead to a real worsening. Certainly, a nocebo procedure is unethical in patients, and this is one of the main reasons much less is known about nocebo phenomena.