Irritable bowel syndrome is regarded as a biopsychosocial disorder, the result of a complex combination of predisposing, precipitating and perpetuating factors. Personality traits, affective status and stress are some of the relevant factors contributing to lower quality of life and symptom exacerbation in IBS patients. In order to examine the role of stress in IBS symptom exacerbation, the aims of this study were to explore the relationship of daily stressful events and symptom severity in a prospective manner and to explore the roles of neuroticism, anxiety, depression and stress in the vicious circle of symptom perpetuation. A total of 49 patients with IBS reported their symptom severity and daily stressful events intensity each day for 14 consecutive days. They also completed the Big five personality inventory, the Beck Depression Inventory and the State-trait anxiety inventory. Cross-correlation analyses were performed on the time series data for daily stress and symptom severity for each participant separately. Four different patterns of relationships were found in different subgroups of participants: positive cross-correlations of symptom severity and stress intensity on the same day; higher symptom severity on days following stressful days; lower symptom severity on days following stressful days; and lower stress intensity on days following severe symptoms. Using average scores for daily stress and symptom severity, as well as scores for neuroticism, anxiety and depression, we performed a path analysis to test a model of symptom exacerbation. It showed that, on the group level, average stress intensity predicts average symptom severity. Neuroticism and anxiety were not significant predictors of symptom severity, while depression showed a marginally significant relationship with symptom severity, mediated by stress intensity. In conclusion, depression and daily stress seem to be important contributors to the vicious circle of IBS symptom perpetuation.