Placebo Effect

Placebos are commonly used in clinical research to validate the efficacy of a therapy. However, placebos represent an excellent model to understand different brain functions and the way mental activity may affect several physiological functions. There is not a single placebo effect, but many, with different mechanisms across different medical conditions and therapeutic interventions. Expectation, anxiety, and reward are all involved, as well as a variety of learning phenomena and genetic variants. The most productive models to better understand the psychobiology of the placebo effect are pain, fatigue, motor disorders, and the immune system. Since the placebo effect is basically a psychosocial context effect, there is now compelling evidence that different social stimuli, such as words and therapeutic rituals, may change the patient's brain, and these effects are similar to those induced by drugs.