Odors and sounds as triggers for medically unexplained symptoms: a fixed-occasion diary study of Gulf War veterans.

BACKGROUND Both laboratory studies on healthy volunteers and epidemiological evidence from patient samples indicate that odor can act as a trigger for the reporting of medically unexplained symptoms (MUSs). PURPOSE The relationship between concurrent experiences of odor and MUSs has not been explored in a patient sample. METHODS This study used an 8-day fixed-occasion diary study, in which 17 veterans of the Persian Gulf War completed diary assessments of (a) the intensity and duration of odor and sound and (b) MUS severity. RESULTS The results showed that the intensity of odor was positively associated with the severity on the same day and subsequent days' symptoms, whereas the duration of odor was negatively related to the severity of MUS reporting on the same day. CONCLUSIONS These results are consistent with an associative mechanism underlying symptom reporting in veterans. By contrast, the duration, but not the intensity, of sound was related to the severity of MUS reporting on the same day.