title: Negative affectivity predicts decreased pain tolerance during low-grade inflammation in healthy women.
abstract: BACKGROUND
  Experimental animal studies provided evidence for a synergistic effect of immunological and psychological stressors on subsequent sickness behaviours. Up to now, little corroborating evidence for such synergy exists for humans, in whom it may provide a mechanism leading to the expression of functional somatic symptoms. The aim of the present study was to determine an interaction between stress(-vulnerability) and an immunological activation on experimental pain sensitivity, i.e., pressure pain threshold and tolerance in healthy humans.
  
  
  METHODS
  In healthy female participants (n=25, mean age 22.3 years), negative affectivity (NA) and experienced stress were assessed by questionnaire before receiving a Salmonella typhi vaccine or saline control in a randomized blinded cross-over design. Pressure pain threshold was assessed at the lower back and calves and pain tolerance was assessed at the thumbnail, before and six hours after each injection.
  
  
  RESULTS
  Vaccination induced leukocytosis (+100%) and increased serum IL-6 (+670%). NA predicted decreased pain tolerance after vaccination (β=-.57, p=.007), but not after placebo (β=.25, p=.26). Post-hoc analyses also demonstrated an association with administration order.
  
  
  CONCLUSIONS
  NA moderated the effects of inflammation on pain tolerance. This finding is consistent with a synergistic model whereby inflammation may lower the threshold for pain reporting in individuals with increased vulnerability for somatic symptom reporting.
authors.affiliation: Department of Clinical and Health Psychology, Utrecht University, Heidelberglaan 1, 3584 CS Utrecht, The Netherlands; Department of Symptom Research, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 1450, Houston, TX 77030, USA. Electronic address: tlacourt@mdanderson.org.
authors.forename: T E
authors.initials: TE
authors.lastname: Lacourt
authors.affiliation: Department of Clinical and Health Psychology, Utrecht University, Heidelberglaan 1, 3584 CS Utrecht, The Netherlands; Department of Psychiatry, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands.
authors.forename: J H
authors.initials: JH
authors.lastname: Houtveen
authors.affiliation: School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: J J C S
authors.initials: JJ
authors.lastname: Veldhuijzen van Zanten
authors.affiliation: School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom; Department of Clinical Psychology, University of Amsterdam, Weesperplein 4, 1018 XA Amsterdam, The Netherlands; Mannheim Institute of Public Health, Social and Preventive Medicine (MIPH), Mannheim Medical Faculty, University of Heidelberg, Ludolf-Krehl-Strasse 7-11, D-68167 Mannheim, Germany.
authors.forename: J A
authors.initials: JA
authors.lastname: Bosch
authors.affiliation: Division of Immunity and Infection, Medical School, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: M T
authors.initials: MT
authors.lastname: Drayson
authors.affiliation: Department of Clinical and Health Psychology, Utrecht University, Heidelberglaan 1, 3584 CS Utrecht, The Netherlands.
authors.forename: L J P
authors.initials: LJ
authors.lastname: Van Doornen
mesh_terms: D000293:Adolescent; D000328:Adult; D000339:Affect; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D007249:Inflammation / Q000523:psychology*; D017288:Pain Threshold / Q000523:psychology*; D012485:Salmonella typhi; D013315:Stress, Psychological; D014611:Vaccination; D055815:Young Adult
keywords: Algometry; Cytokines; Experimental pain; Human; Inflammation; Inflammatory response; Interleukin-6; Life events; Negative affect; Negative affectivity; Pain sensitivity; Pain threshold; Pain tolerance; Placebo; Pressure pain; Randomized control; Stress; Vaccine