title: Placebo 'serotonin' increases heart rate variability in recovery from psychosocial stress.
abstract: OBJECTIVE
  To investigate placebo effects on heart rate (HR) and heart rate variability (HRV) in recovery from a psychosocial stressor.
  
  
  METHODS
  A healthy sample underwent two mental arithmetic stress tests in one experimental session. After undergoing the baseline test, participants were randomized into control or placebo groups. Prior to the second stress test, the placebo group received an intranasal dose of 'serotonin' (placebo) with the suggestion that it would enhance recovery. HR and HRV were assessed throughout procedures.
  
  
  RESULTS
  There was an increase in vagally-mediated HRV in the placebo group. The change in HR did not differ between groups.
  
  
  CONCLUSIONS
  Placebo suggestion can enhance autonomic recovery after psychosocial stress. Findings are consistent with the notion of top-down mechanisms of placebo effects, but further research would need to specifically examine the role of top-down regulatory pathways as possible mediators of placebo-induced changes in autonomic function.
authors.affiliation: The University of Auckland, New Zealand. Electronic address: m.darragh@auckland.ac.nz.
authors.forename: Margot
authors.initials: M
authors.lastname: Darragh
authors.affiliation: The University of Auckland, New Zealand. Electronic address: t.vanderboor@gmail.com.
authors.forename: Teresa
authors.initials: T
authors.lastname: Vanderboor
authors.affiliation: The University of Auckland, New Zealand. Electronic address: rj.booth@auckland.ac.nz.
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Booth
authors.affiliation: The University of Auckland, New Zealand. Electronic address: j.sollers@auckland.ac.nz.
authors.forename: John J
authors.initials: JJ
authors.lastname: Sollers
authors.affiliation: The University of Auckland, New Zealand. Electronic address: n.consedine@auckland.ac.nz.
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Consedine
mesh_terms: D000281:Administration, Intranasal; D000293:Adolescent; D000328:Adult; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D015990:Placebo Effect; D020127:Recovery of Function / Q000187:drug effects*; D012701:Serotonin / Q000008:administration & dosage*; D017366:Serotonin Receptor Agonists / Q000008:administration & dosage*; D018709:Statistics, Nonparametric; D013315:Stress, Psychological / Q000188:drug therapy*; D055815:Young Adult
chemical_list: D017366:Serotonin Receptor Agonists; D012701:Serotonin
keywords: Autonomic nervous system; Heart rate variability; Neurovisceral integration model; Placebo effect; Stress