Background <p>Childhood trauma and negative events during adulthood were associated with the symptom severity of irritable bowel syndrome (IBS). However, the interaction effect of these negative events on IBS remains poorly understood.</p> Methods <p>70 healthy individuals who completed Childhood Trauma Questionnaire (CTQ) and Life Event Scale (LES) and 88 IBS patients, diagnosed based on the Rome IV criteria, who completed CTQ, LES, IBS-Quality of Life (IBS-QOL), and IBS-Severity Scoring System (IBS-SSS) were retrospectively included. Logistic and linear regression analyses were used to investigate the interaction effect between childhood trauma and negative events during adulthood on IBS.</p> Results <p>Female sex, childhood emotional abuse and neglect, and negative events during adulthood were associated with a higher prevalence of IBS. In IBS patients, childhood emotional abuse and neglect, as well as negative events during adulthood, were independently associated with more severe symptoms and worse quality of life. A significant interaction effect between childhood emotional trauma and negative events during adulthood was observed in IBS severity and quality of life, though no interaction effect was found in IBS development. Subsequent analyses revealed that the effect of negative events during adulthood on IBS severity and quality of life increased in IBS patients with childhood emotional trauma (IBS-SSS, β = 5.75, <i>p</i> &lt; 0.001; IBS-QOL, β = 2.1, <i>p</i> &lt; 0.001) compared with those without (IBS-SSS, β = 3.23, <i>p</i> &lt; 0.001; IBS-QOL, β = 0.69, <i>p</i> = 0.011).</p> Conclusions <p>Childhood emotional trauma and negative events during adulthood were associated with IBS development, higher IBS severity, and worse quality of life. Furthermore, childhood emotional trauma increased the negative effect of negative events during adulthood on IBS severity and quality of life.</p>