Nocebo Effect

Nocebo effects may account for 38% to 100% of adverse events reported in clinical trials. Nocebo effects may involve psychosomatic mechanisms in which anxious feelings trigger biological responses. Withholding information about possible side effects during informed consent is uncommon and ethically difficult. Nocebo effects are described as persistent and difficult to eliminate. Side-effect information can increase anxiety, reduce adherence and contribute to treatment discontinuation. Psychologically sensitive symptoms including pain, fatigue, nausea and itching are especially likely to be influenced by the nocebo effect. Patient information leaflets describing side effects may contribute to nocebo development.