Odors eliciting fear: A conditioning approach to Idiopathic Environmental Intolerances

• Published in: Journal of behavior therapy and experimental psychiatry 2011-06, Vol.42 (2), p.240-249
• Main Authors: Leer, Arne, Smeets, Monique A.M, Bulsing, Patricia J, van den Hout, Marcel A
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Avoidance behavior; Avoidance Learning - physiology; Biological and medical sciences; Biological organs; Conditioning; Conditioning (Psychology); Electrodermal response; Environment; Extinction, Psychological - physiology; Fear; Fear - physiology; Fear - psychology; Female; Fundamental and applied biological sciences. Psychology; Galvanic skin response; Hedonic differences; Human; Human fear conditioning; Humans; Idiopathic; Learning. Memory; Male; Multiple Chemical Sensitivity - psychology; Odor; Odorants; Psychiatry; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Sniffing; Unpleasant
• ISSN: 0005-7916; 1873-7943
• DOI: 10.1016/j.jbtep.2010.12.007

Abstract Patients suffering from Idiopathic Environmental Intolerances (IEI) report health symptoms, referable to multiple organ systems, which are triggered by harmless odors and therefore medically unexplainable. In line with previous research that predominantly points towards psychological explanations, the present study tests the hypothesis that IEI symptoms result from learning via classical conditioning of odors to fear. A differential conditioning paradigm was employed. Hedonically different odors were compared on ease of fear acquisition. Conditioned stimuli (CSs) were Dimethyl Sulfide (unpleasant) and peach (pleasant). The unconditioned stimulus (US) was an electrical shock. During acquisition one odor (CS+) was followed by shock, while the other odor (CS−) was not. Next, fear extinction was tested by presenting both CS+ and CS− without US. Electrodermal response, odor evaluation, and sniffing behavior were monitored. Results showed successful fear conditioning irrespective of hedonic character as evidenced by electrodermal response. Acquired fear did not extinguish. There was no evidence of evaluative conditioning taking place, as CS evaluation did not change during fear acquisition. Early avoidance of the CS+, as deduced from odor inhalation measures, was demonstrated, but did not sustain during the entire acquisition phase. This study suggests that a fear conditioning account of IEI is only partially satisfactory.