title: Consistency of the placebo effect.
abstract: OBJECTIVE
  The existence of reliable personality predictors of the placebo effect is controversial. For prediction to be possible, the response to placebo must be reliable. We tested the consistency of the placebo effect by assessing the response to four trials of placebo analgesic treatment.
  
  
  METHODS
  Two identical experimental pain stimuli were administered simultaneously to matching fingers on both hands. Pain sensation was compared between one finger, which was treated with a placebo cream and the other which was not treated. Two placebo creams were used, each with a different label. The procedure was repeated between 1 and 8 days later using the same creams and order of presentation. Two personality traits (acquiescence and absorption) and response expectancy were assessed as potential predictors of the placebo effect.
  
  
  RESULTS
  Placebo effects across trials were highly correlated (r=.60 and .77) when placebos bore the same name but were not significantly correlated when placebos had different names. Placebo effects were significantly associated with response expectancy but not with acquiescence or absorption.
  
  
  CONCLUSIONS
  Context-specific predictions of placebo response (e.g., expectancy) are possible, but personality predictors will not be consistent across contexts.
authors.affiliation: School of Psychology, University of Plymouth, Plymouth, UK.
authors.forename: Ben
authors.initials: B
authors.lastname: Whalley
authors.forename: Michael E
authors.initials: ME
authors.lastname: Hyland
authors.forename: Irving
authors.initials: I
authors.lastname: Kirsch
mesh_terms: D000328:Adult; D000700:Analgesics / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008297:Male; D010146:Pain / Q000188:drug therapy*; D015990:Placebo Effect
chemical_list: D000700:Analgesics