title: Gender differences in placebo analgesia: event-related potentials and emotional modulation.
abstract: OBJECTIVE
  To examine whether there are gender differences in event-related potential (ERP) responses to painful stimulation after administration of placebo medication; and to investigate whether placebo medication reduces anticipatory stress and if this reduction can explain the placebo analgesic response. Several experimental and clinical studies have shown that males report lower pain compared with females. There are, however, few reports of gender differences in placebo analgesia.
  
  
  METHODS
  All subjects (n = 33; 17 women) participated in both a natural history and a placebo condition. ERPs were evoked by heat pulses with a peak at 52 °C.
  
  
  RESULTS
  The results showed that pain unpleasantness and the N2/P2 ERP components were reduced in the placebo condition compared with the natural history condition. Only men displayed placebo responses in pain report and in the P2 component. Anticipatory stress was reduced after placebo administration, and the reduction in anticipatory stress was significantly related to the placebo effect on pain. Regression analyses revealed that the interaction of gender by anticipatory stress was significantly related to the mean placebo response, with men responding with lower stress after placebo medication, and larger placebo responses.
  
  
  CONCLUSIONS
  A placebo response on pain unpleasantness was observed in men only, and reduced stress after placebo administration was observed in males only. Thus, reduced stress may be a mechanism for placebo responses in pain.
authors.affiliation: Department of Psychology, University of Tromsø, 9037 Tromsø, Norway. per-matti.aslaksen@uit.no
authors.forename: Per M
authors.initials: PM
authors.lastname: Aslaksen
authors.forename: Martin
authors.initials: M
authors.lastname: Bystad
authors.forename: Sara M
authors.initials: SM
authors.lastname: Vambheim
authors.forename: Magne A
authors.initials: MA
authors.lastname: Flaten
mesh_terms: D000328:Adult; D000698:Analgesia / Q000379:methods / Q000523:psychology*; D000700:Analgesics / Q000627:therapeutic use; D004569:Electroencephalography / Q000379:methods / Q000706:statistics & numerical data; D004644:Emotions / Q000502:physiology*; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D010146:Pain / Q000523:psychology*; D010147:Pain Measurement / Q000379:methods / Q000523:psychology; D058748:Pain Perception / Q000502:physiology*; D017288:Pain Threshold / Q000502:physiology; D010812:Physical Stimulation; D015990:Placebo Effect; D017678:Sex Distribution; D012737:Sex Factors; D013001:Somatoform Disorders / Q000188:drug therapy
chemical_list: D000700:Analgesics