It is well known that mental stress often induces gastrointestinal (GI) symptoms, such as abdominal pain, nausea and diarrhea. Irritable bowel syndrome (IBS) is one of the most common diseases, characterized by abdominal pain associated with altered bowel habit, such as diarrhea, constipation or both. Abnormality in brain-gut axis, autonomic dysregulation, visceral hypersensitivity, or altered emotional processing is considered to be the important contributing factor in the pathogenesis of IBS. However, precise pathophysiology of IBS is still complex and not completely understood. To clarify the role of reactivity to stress in the pathogenesis of IBS, characteristics of autonomic responses to physical (cold pressor test) and psychological (Stroop color–word conflict test) stimuli were examined, along with the mood change associated with the stimuli, in female college students with gastrointestinal symptoms (who met Rome III criteria for IBS, without checkup for gastrointestinal organic diseases). Mood states were estimated by a profile of mood states, and autonomic nervous function was evaluated by a spectral analysis of heart rate variability (HRV), baroreflex sensitivity, and systolic and diastolic blood pressure. Repeated measures analysis of variance (ANOVA) revealed significant interaction of group (females with GI symptoms and healthy controls)×time course after the psychological stimulus in HF amplitude of HRV, that is, delayed and attenuated recovery after the Stroop color–word conflict test in females with GI symptoms. Repeated measures ANOVA also revealed significant main effect of group in baroreflex sensitivity, that is, the baroreflex sensitivity is generally lower in females with GI symptoms, though the time courses in both groups were similar. Prestimulus basal level of tension-anxiety were significantly higher in females with GI symptoms compared to controls. These results suggest that attenuated and delayed recovery from psychological stimuli may indicate altered emotional processing which could contribute to various gastrointestinal and psychological symptoms.
Keywords: Irritable bowel syndrome, heart rate variability, profile of mood states, cold pressor test, stroop color–word conflict test