[Placebo response - Mechanisms and clinical applications]

Research on placebo responses has made major progress in recent years. Placebo responses are psychobiological events, which are created by the entire therapeutic context. They can appear at any time, not only in experimental and clinical settings. Several studies on analgesia-related placebo research showed that patients have higher placebo responses in comparison to healthy participants, which may also last longer. Expectations play a key role in placebo analgesia. They can be induced via three central psychological mechanisms: 1) expectation induced via instructions, 2) expectation induced via classical conditioning and 3) expectation induced via social learning. These mechanisms are controlled by neurobiological structures and modulate pain perception resulting in pain relief by positive expectations and increased pain by negative expectations, the so-called nocebo effect. There is an ongoing discussion that these psychological mechanisms may also play a central role in inducing and maintaining itch-reducing placebo responses. The current state of research suggests that placebo responses could be used in clinical contexts and should not be viewed as being in competition with medications but as an additive increase in efficacy of a pharmacological substance through specifically induced placebo responses. This targeted use is also possible within ethical guidelines. Important prerequisites are that the research results can be transferred from healthy participants to patients and that the placebo responses are reproducible.