nocebo effect

Definition of nocebo effect

nocebo effect (noh-SEE-boh eh-FEKT): A situation in which a patient develops side effects or symptoms that can occur with a drug or other therapy just because the patient believes they may occur. For example, in a clinical trial, patients who are not given an active treatment, but are told what side effects the active treatment may cause, may have the same side effects as the patients who are given the active treatment, only because they expect them to occur.

Source: NCI Dictionary of Cancer Terms