title: Perceived treatment group affects behavioral and neural responses to visceral pain in a deceptive placebo study.
abstract: BACKGROUND
  To assess effects of perceived treatment (i.e. drug vs placebo) on behavioral and neural responses to rectal pain stimuli delivered in a deceptive placebo condition.
  
  
  METHODS
  This fMRI study analyzed the behavioral and neural responses during expectation-mediated placebo analgesia in a rectal pain model. In N = 36 healthy subjects, the blood oxygen level-dependent (BOLD) response during cued anticipation and painful stimulation was measured after participants were informed that they had a 50% chance of receiving either a potent analgesic drug or an inert substance (i.e., double-blind administration). In reality, all received placebo. We compared responses in subjects who retrospectively indicated that they received the drug and those who believed to have received placebo.
  
  
  RESULTS
  55.6% (N = 20) of subjects believed that they had received a placebo, whereas 36.1% (N = 13) believed that they had received a potent analgesic drug. Subjects who were uncertain (8.3%, N = 3) were excluded. Rectal pain-induced discomfort was significantly lower in the perceived drug treatment group (P < 0.05), along with significantly reduced activation of the insular, the posterior and anterior cingulate cortices during pain anticipation, and of the anterior cingulate cortex during pain (all P < 0.05 in regions-of-interest analyses).
  
  
  CONCLUSIONS
  Perceived treatment constitutes an important aspect in placebo analgesia. A more refined understanding of individual treatment expectations and perceived treatment allocation has multiple implications for the design and interpretation of clinical trials and experimental studies on placebo and nocebo effects.
authors: Institute of Medical Psychology and Behavioral Immunobiology, University Hospital of Essen, University of Duisburg-Essen, Essen, Germany.
authors: V
authors: V
authors: Kotsis
authors: S
authors: S
authors: Benson
authors: U
authors: U
authors: Bingel
authors: M
authors: M
authors: Forsting
authors: M
authors: M
authors: Schedlowski
authors: E R
authors: ER
authors: Gizewski
authors: S
authors: S
authors: Elsenbruch
mesh_terms: D000328:Adult; D000700:Analgesics / Q000494:pharmacology; D059031:Anticipation, Psychological / Q000502:physiology*; D001921:Brain / Q000187:drug effects* / Q000502:physiology; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010147:Pain Measurement; D015990:Placebo Effect; D059265:Visceral Pain / Q000188:drug therapy / Q000523:psychology*
chemical_list: D000700:Analgesics