The placebo-nocebo response: controversies and challenges from clinical and research perspective.

Placebo and nocebo responses fascinate, confuse, mystify and challenge. They are genuine social, cultural and psychobiological phenomena which can significantly modify the overall treatment outcome. The placebo-nocebo phenomenon represents a very good model for our better understanding the role of treatment context and how the words, indices, symbols and icons act on our brains. Placebo response is associated with reward expectancy and relief of anticipatory anxiety, while nocebo response is related to lack of reward/positive expectancy and to increase of anticipatory anxiety. Placebo-nocebo responses are mediated through changes in various cortico-subcortical networks and psychophysiological systems. In spite of many existing complementary theories and still growing research on placebo and nocebo response, the implementation of our current knowledge to benefit basic research, clinical trials and routine clinical practice is still so scarce.