Irritable bowel syndrome (IBS) is a functional disease with no exact laboratory or imaging findings. IBS is more common in areas with a history of psychological trauma and war. This study aims to report the prevalence and possible determinants of IBS in southwestern Iran, an area with a notable history of war.

We randomly enrolled 1849 permanent residents in 29 cities aged 20 to 65 years. A validated for Farsi version Rome III criteria and a questionnaire, including demographic data and health history, were administered to each subject. Participants who fulfilled the Rome III criteria were categorized into three groups: Diarrhea dominant (IBS-D), Constipation dominant (IBS-C), and Mixed type (IBS-M).

The total prevalence of IBS was 3.2%, with 70% of subjects being of Arab descent (P = 0.004). IBS was more common in females, singles, illiterate subjects, and people younger than 30 years; however, none of these differences were statistically significant. People with depression, anxiety, self-report of psychological disorders, and very low socioeconomic status had a significantly higher prevalence of IBS (P < 0.05). After multivariable logistic regression analysis, very low socioeconomic status had an independent role in IBS predictivity (OR: 2.28, 95% CI: 1.01–5.15).

This study shows a higher prevalence of IBS symptoms in a population-based study in the region compared to counterparts in other regions of Iran. Considering the higher prevalence of self-reported psychological disorders, further studies are recommended to focus on the exact diagnosis of mental disorders and their influence on IBS.