title: Effects of subtle cognitive manipulations on placebo analgesia - An implicit priming study.
abstract: Expectancy is widely accepted as a key contributor to placebo effects. However, it is not known whether non-conscious expectancies achieved through semantic priming may contribute to placebo analgesia. In this study, we investigated if an implicit priming procedure, where participants were unaware of the intended priming influence, affected placebo analgesia.
  
  
  
  In a double-blind experiment, healthy participants (n = 36) were randomized to different implicit priming types; one aimed at increasing positive expectations and one neutral control condition. First, pain calibration (thermal) and a credibility demonstration of the placebo analgesic device were performed. In a second step, an independent experimenter administered the priming task; Scrambled Sentence Test. Then, pain sensitivity was assessed while telling participants that the analgesic device was either turned on (placebo) or turned off (baseline). Pain responses were recorded on a 0-100 Numeric Response Scale.
  
  
  
  Overall, there was a significant placebo effect (p < 0.001), however, the priming conditions (positive/neutral) did not lead to differences in placebo outcome. Prior experience of pain relief (during initial pain testing) correlated significantly with placebo analgesia (p < 0.001) and explained 34% of placebo variance. Trait neuroticism correlated positively with placebo analgesia (p < 0.05) and explained 21% of placebo variance.
  
  
  
  Priming is one of many ways to influence behaviour, and non-conscious activation of positive expectations could theoretically affect placebo analgesia. Yet, we found no SST priming effect on placebo analgesia. Instead, our data point to the significance of prior experience of pain relief, trait neuroticism and social interaction with the treating clinician.
  
  
  
  Our findings challenge the role of semantic priming as a behavioural modifier that may shape expectations of pain relief, and affect placebo analgesia.
authors.affiliation: Department of Clinical Neuroscience, Osher Center for Integrative Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Rosén
authors.affiliation: Department of Clinical Neuroscience, Osher Center for Integrative Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Yi
authors.affiliation: Program in Placebo Studies and Therapeutic Encounters, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, USA.
authors.forename: I
authors.initials: I
authors.lastname: Kirsch
authors.affiliation: Program in Placebo Studies and Therapeutic Encounters, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Kaptchuk
authors.affiliation: Department of Clinical Neuroscience, Osher Center for Integrative Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Ingvar
authors.affiliation: Department of Clinical Neuroscience, Osher Center for Integrative Medicine, Karolinska Institutet, Stockholm, Sweden.|Program in Placebo Studies and Therapeutic Encounters, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, USA.
authors.forename: K B
authors.initials: KB
authors.lastname: Jensen
mesh_terms: D000293:Adolescent; D000328:Adult; D000698:Analgesia / Q000379:methods*; D003071:Cognition; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000523:psychology*; D059408:Pain Management / Q000379:methods*; D010147:Pain Measurement; D017288:Pain Threshold; D015990:Placebo Effect; D055815:Young Adult