Clinical and ethical implications of placebo effects: enhancing patients' benefits from pain treatment.

Expectancy and learning are the core psychological mechanisms of placebo analgesia. They interact with further psychological processes such as emotions and motivations (e.g., anxiety, desire for relief), somatic focus, or cognitions (e.g., attitudes toward the treatment). The development of placebo responsiveness and the actual placebo response in a person is the result of the complex interaction between factors traced back to the individual learning history related to analgesic drugs or treatments and factors of the current context referring to the analgesic or placebo treatment. The aim of this chapter is to depict these complex interactions in a new model of analgesic placebo effects. It joins aspects of the learning history (preexisting experiences and preexisting expectations) of a patient with aspects of the current context (current expectation as a result of external and internal situation in which a pain medication/treatment/placebo is taken, e.g., current information about pain medication, current specific context/cues, desire for pain relief, certainty about upcoming pain relief, current expectation about pain reducing course, current selective attention, increased pain experience, or decreased pain experience). In order to exploit placebo efficacy for an analgesic treatment it is worthwhile to assess in which direction each of these factors exerts its influence in order to maximize placebo effects for a specific patient. By applying placebo mechanisms in this differentiated way, the efficacy of pain treatment can be deliberately boosted.