title: Learning to have psychosomatic complaints: conditioning of respiratory behavior and somatic complaints in psychosomatic patients.
abstract: OBJECTIVE
  Assuming a subjective similarity between the experience of a hyperventilation episode and inhaling CO2-enriched air, we tested whether a respiratory challenge in association with a particular stimulus could result in altered respiratory behavior and associated somatic complaints upon presenting the stimulus only.
  
  
  METHODS
  Psychosomatic patients (N = 28) reporting hyperventilation complaints participated in a differential conditioning paradigm using odors with a positive or negative valence as conditioned stimuli (CS+ or CS-) and 7.4% CO2-enriched air as the unconditioned stimulus (US). Three CS+ and three CS-acquisition trials were run. During the test phase, two CS(+)- and two CS(-)-only trials were run, followed by two new test odors (with a positive or negative valence). Respiratory frequency, tidal volume, end-tidal fractional concentration of CO2, and heart rate were measured throughout the experiment. Somatic complaints were registered after each trial.
  
  
  RESULTS
  We observed a) increased respiratory frequency and an elevated level of somatic complaints upon presenting the CS+ only; b) a selective association effect: conditioning was only apparent with the negatively valenced CS+ odor; (c) no generalization of respiratory responses and complaints to the new odors; (d) no conditioning effect on dummy complaints that are usually not reported when inhaling CO2; (e) in exploratory comparisons with normal subjects, stronger conditioning effects on typical hyperventilation complaints in patients, and, in female subjects, on respiratory frequency.
  
  
  CONCLUSIONS
  Respiratory responses and psychosomatic complaints can be elicited by conditioned stimuli in a highly specific way. The findings are relevant for disorders in which respiratory abnormalities and/or psychosomatic complaints may play a role and for multiple chemical sensitivity.
authors.affiliation: Department of Psychology, University of Leuven, Belgium.
authors.forename: O
authors.initials: O
authors.lastname: Van den Bergh
authors.forename: K
authors.initials: K
authors.lastname: Stegen
authors.forename: K P
authors.initials: KP
authors.lastname: Van de Woestijne
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002245:Carbon Dioxide / Q000009:adverse effects; D016022:Case-Control Studies; D003214:Conditioning, Classical; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology* / Q000523:psychology*; D008297:Male; D008875:Middle Aged; D009812:Odorants; D011602:Psychophysiologic Disorders / Q000209:etiology*; D012044:Regression Analysis; D012129:Respiratory Function Tests; D012737:Sex Factors; D012803:Sick Role
chemical_list: D002245:Carbon Dioxide