Abstract
OBJECTIVES: Multiple chemical sensitivity is a poorly understood syndrome in which various symptoms are triggered by chemically unrelated, but often odorous substances, at doses below those known to be harmful. This study focuses on the process of pavlovian acquisition and extinction of somatic symptoms triggered by odours. METHODS: Diluted ammonia and butyric acid were odorous conditioned stimuli (CS). The unconditioned stimulus (US) was 7.4% CO2 enriched air. One odour (CS+) was presented together with the US for 2 minutes (CS+ trial), and the other odour (CS-) was presented with air (CS-trial). Three CS+ and three CS-exposures were run in a semi-randomised order; this as the acquisition (conditioning) phase. To test the effect of the conditioning, each subject then had one CS+ only--that is, CS+ without CO2--and one CS- test exposure. Next, half the subjects (n = 32) received five additional CS+ only exposures (extinction group), while the other half received five exposures to breathing air (wait group). Finally, all subjects got one CS+ only test exposure to test the effect of the extinction. Ventilatory responses were measured during and somatic symptoms after each exposure. RESULTS: More symptoms were reported upon exposure to CS+ only than to CS-odours, regardless of the odour type. Altered respiratory rate was only found when ammonia was CS+. Five extinction trials were sufficient to reduce the level of acquired symptoms. CONCLUSION: Subjects can acquire somatic symptoms and altered respiratory behaviour in response to harmless, but odorous chemical substances, if these odours have been associated with a physiological challenge that originally had caused these symptoms. The conditioned symptoms can subsequently be reduced in an extinction procedure. The study further supports the plausibility of a pavlovian conditioning hypothesis to explain the pathogenesis of MCS.
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Selected References
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- Bolla-Wilson K., Wilson R. J., Bleecker M. L. Conditioning of physical symptoms after neurotoxic exposure. J Occup Med. 1988 Sep;30(9):684–686. [PubMed] [Google Scholar]
- Cullen M. R. The worker with multiple chemical sensitivities: an overview. Occup Med. 1987 Oct-Dec;2(4):655–661. [PubMed] [Google Scholar]
- Guglielmi R. S., Cox D. J., Spyker D. A. Behavioral treatment of phobic avoidance in multiple chemical sensitivity. J Behav Ther Exp Psychiatry. 1994 Sep;25(3):197–209. doi: 10.1016/0005-7916(94)90020-5. [DOI] [PubMed] [Google Scholar]
- Hamm A. O., Vaitl D., Lang P. J. Fear conditioning, meaning, and belongingness: a selective association analysis. J Abnorm Psychol. 1989 Nov;98(4):395–406. doi: 10.1037//0021-843x.98.4.395. [DOI] [PubMed] [Google Scholar]
- Hornsveld H. K., Garssen B., Dop M. J., van Spiegel P. I., de Haes J. C. Double-blind placebo-controlled study of the hyperventilation provocation test and the validity of the hyperventilation syndrome. Lancet. 1996 Jul 20;348(9021):154–158. doi: 10.1016/s0140-6736(96)02024-7. [DOI] [PubMed] [Google Scholar]
- Lehrer P. M. Psychophysiological hypotheses regarding multiple chemical sensitivity syndrome. Environ Health Perspect. 1997 Mar;105 (Suppl 2):479–483. doi: 10.1289/ehp.97105s2479. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Miller C. S. White paper: Chemical sensitivity: history and phenomenology. Toxicol Ind Health. 1994 Jul-Oct;10(4-5):253–276. [PubMed] [Google Scholar]
- Shusterman D. Critical review: the health significance of environmental odor pollution. Arch Environ Health. 1992 Jan-Feb;47(1):76–87. doi: 10.1080/00039896.1992.9935948. [DOI] [PubMed] [Google Scholar]
- Siegel S., Kreutzer R. Pavlovian conditioning and multiple chemical sensitivity. Environ Health Perspect. 1997 Mar;105 (Suppl 2):521–526. doi: 10.1289/ehp.97105s2521. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sparks P. J., Daniell W., Black D. W., Kipen H. M., Altman L. C., Simon G. E., Terr A. I. Multiple chemical sensitivity syndrome: a clinical perspective. II. Evaluation, diagnostic testing, treatment, and social considerations. J Occup Med. 1994 Jul;36(7):731–737. [PubMed] [Google Scholar]
- Van den Bergh O., Stegen K., Van de Woestijne K. P. Learning to have psychosomatic complaints: conditioning of respiratory behavior and somatic complaints in psychosomatic patients. Psychosom Med. 1997 Jan-Feb;59(1):13–23. doi: 10.1097/00006842-199701000-00003. [DOI] [PubMed] [Google Scholar]
- Van den Bergh O., Stegen K., Van de Woestijne K. P. Memory effects on symptom reporting in a respiratory learning paradigm. Health Psychol. 1998 May;17(3):241–248. doi: 10.1037//0278-6133.17.3.241. [DOI] [PubMed] [Google Scholar]
- Wientjes C. J., Grossman P. Overreactivity of the psyche or the soma? Interindividual associations between psychosomatic symptoms, anxiety, heart rate, and end-tidal partial carbon dioxide pressure. Psychosom Med. 1994 Nov-Dec;56(6):533–540. doi: 10.1097/00006842-199411000-00009. [DOI] [PubMed] [Google Scholar]
- Ziem G. E., Davidoff L. L. Illness from chemical "odors": is the health significance understood? Arch Environ Health. 1992 Jan-Feb;47(1):88–91. doi: 10.1080/00039896.1992.9935949. [DOI] [PubMed] [Google Scholar]
- van den Bergh O., Kempynck P. J., van de Woestijne K. P., Baeyens F., Eelen P. Respiratory learning and somatic complaints: a conditioning approach using CO2-enriched air inhalation. Behav Res Ther. 1995 Jun;33(5):517–527. doi: 10.1016/0005-7967(94)00080-4. [DOI] [PubMed] [Google Scholar]