Perceived relation between odors and a negative event determines learning of symptoms in response to chemicals.
BACKGROUND
We investigated the effects of worrying information about chemical pollution on subjective symptoms in response to an odor that was previously associated with symptom episodes.


METHODS
Ammonia and butyric acid in harmless concentrations were used as odor cues, and 10% CO2-enriched air was used to induce symptoms. One of two odors was consistently mixed with CO2-enriched air while the other odor was presented in room air during 80 s breathing trials (three trials of each). Next, information framing the experiment in the context of possible health-damaging effects of chemical pollution of our environment was presented to half the participants, whereas no information was given to the other half. Finally, both odor cues were presented with room air. Symptom scores were used as the dependent variable.


RESULTS
Unexpectedly, participants reported more symptoms in response to the odor previously presented with air than to the odor previously presented with CO2-enriched air. Post-hoc analyses suggested a crucial role for perceived rather than actual contingencies between odor and symptom episodes. Information manipulation had no effect.


CONCLUSIONS
Believing that a specific odor cue was associated with a symptom episode was more important than the actual association in order to provoke symptoms in response to harmless odor cues.
Devriese
Stephan
S
Research Group for Stress, Health, and Well-being, Faculty of Psychology and Educational Sciences, University of Leuven, Tiensestraat 102, 3000, Leuven, Belgium. stephan.devriese@psy.kuleuven.ac.be
Winters
Winnie
W
Van Diest
Ilse
I
De Peuter
Steven
S
Vos
Gerrit
G
Van de Woestijne
Karel
K
Van den Bergh
Omer
O
D000293:Adolescent; D000328:Adult; D000393:Air Pollutants; D001530:Belgium; D006801:Humans; D018777:Multiple Chemical Sensitivity / Q000503:physiopathology; D009812:Odorants; D012016:Reference Values; D012903:Smell
D000393:Air Pollutants