[Placebo Responses in Chronic Pain: State of Research and Clinical Implications]

Placebo hypoalgesia has been found to play an important role in every health care by modulating patients' responses to pharmacologically active analgesic treatments. It may be seen as reflecting the capacity for endogenous pain modulation. Enhancing the efficacy of analgesic treatments by boosting endogenous pain modulation might be particularly relevant for chronic pain patients. Research into placebo hypoalgesic responses to chronic pain is sparse, however. In healthy subjects, placebo hypoalgesia is induced by expectations of pain relief through verbal information and learning experiences. Here we review the existing evidence on placebo hypoalgesia to chronic pain. To our knowledge, placebo hypoalgesia to chronic pain has been investigated experimentally in chronic back and chronic musculoskeletal pain, neuropathic pain after thoracotomy, and episodic migraine. Results point towards a maintenance of placebo hypoalgesic responses in chronic pain populations, thus highlighting the potential benefit of boosting placebo hypoalgesic responses in the treatment of chronic pain. Strategies on boosting placebo hypoalgesic responses in every day healthcare are presented.