Objective: The individual occurrence of depression or insomnia is a risk factor for irritable bowel syndrome (IBS), but few researchers have evaluated the association between comorbid depression and insomnia and IBS. The aim of the present study is to explore the relationship between IBS and the coexistence of depression and insomnia in a Korean population-based cohort study. Methods: A total of 3429 individuals who were enrolled in the Korean Genome and Epidemiology Study were analysed. Of the participants, 10.9% (n = 374) were diagnosed with IBS based on the Rome II criteria. Regarding depressive symptoms, subjects were sub-divided into three groups based on the Beck Depression Inventory (BDI) score. Insomnia was defined as a positive response to at least one of three questions on sleep states. Results: The odds ratio (OR) of IBS increased proportionally as depressive symptoms worsened (OR: 1.64; 95% Cl: 121-2.23 in middle tertile and OR: 2.61; 95% Cl: 1.92-3.55 in highest tertile). Subjects with insomnia showed a higher OR of IBS than those without insomnia (OR: 1.81; 95% Cl: 1.44-2.27). In the joint analysis of BDI and insomnia, the odds for IBS were significantly higher in all BDI tertiles with insomnia than in the corresponding BDI tertiles without insomnia. There was no significant interaction effect of BDI tertile and insomnia on IBS. Conclusion: The presence of both depression and insomnia is significantly associated with IBS compared to each individual occurrence. Further prospective investigations are needed to explore possible causality between co-morbid depression and insomnia and IBS. (C) 2016 Elsevier Inc. All rights reserved.