ObjectiveThis cross-sectional study aimed to explore the associations among childhood trauma, inflammation and depressive severity, with a particular focus on the mediating role of a peripheral blood inflammatory marker (the Aggregate Index of Systemic Inflammation, AISI) in the relationship between childhood emotional neglect and depressive severity.MethodsA total of 236 patients with major depressive disorder (MDD) were enrolled in this study. All participants completed the Childhood Trauma Qu