title: Placebo effects and their determinants in gastrointestinal disorders.
abstract: Placebo effects in clinical trials have sparked an interest in the placebo phenomenon, both in randomized controlled trials (RCTs) and in experimental gastroenterology. RCTs have demonstrated similar short-term and long-term placebo response rates in gastrointestinal compared to other medical diagnoses. Most mediators and moderators of placebo effects in gastrointestinal diseases are also of similar type and size to other medical diagnoses and not specific for gastrointestinal diagnoses. Other characteristics such as an increase in the placebo response over time and the placebo-enhancing effects of unbalanced randomization were not seen, at least in IBS. Experimental placebo and nocebo studies underscore the 'power' of expectancies and conditioning processes in shaping gastrointestinal symptoms not only at the level of self-reports, but also within the brain and along the brain-gut axis. Brain imaging studies have redressed earlier criticism that placebo effects might merely reflect a response bias. These findings raise hope that sophisticated trials and experiments designed to boost positive expectations and minimize negative expectations could pave the way for a practical and ethically sound use of placebo knowledge in daily practice. Rather than focusing on a 'personalized' choice of drugs based on biomarkers or genes, it might be the doctor-patient communication that needs to be tailored.
authors.affiliation: Institute of Medical Psychology &Behavioural Immunobiology, University Hospital Essen, University of Duisburg-Essen, Hufelandstrasse 55, 45122 Essen, Germany.
authors.forename: Sigrid
authors.initials: S
authors.lastname: Elsenbruch
authors.affiliation: Department of Internal Medicine VI, Psychosomatic Medicine and Psychotherapy, University Hospital, Tübingen University, Frondsbergstrasse 23, 72076 Tübingen, Germany.
authors.forename: Paul
authors.initials: P
authors.lastname: Enck
mesh_terms: D000328:Adult; D000367:Age Factors; D059031:Anticipation, Psychological; D002648:Child; D005260:Female; D005512:Food Hypersensitivity / Q000523:psychology / Q000628:therapy; D005767:Gastrointestinal Diseases / Q000235:genetics / Q000523:psychology / Q000628:therapy*; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000523:psychology / Q000628:therapy; D007858:Learning; D008297:Male; D015201:Meta-Analysis as Topic; D009325:Nausea / Q000523:psychology / Q000628:therapy; D010551:Personality; D015990:Placebo Effect; D011110:Polymorphism, Genetic; D016032:Randomized Controlled Trials as Topic; D012737:Sex Factors; D013997:Time Factors; D059265:Visceral Pain / Q000523:psychology / Q000628:therapy; D055815:Young Adult