Background <p>Childhood trauma is a distal risk for depression, potentially mediated by psychological factors including cognitive vulnerability and perceived stress. This study aimed to clarify the directional pathway and test the temporal stability of the mediation involving cognitive vulnerability and perceived stress between childhood trauma and depression.</p> Methods <p>A total of 1,798 Chinese university students (65.80% female) completed baseline assessments using the Childhood Trauma Questionnaire, Cognitive Style Questionnaire–Short Form, Perceived Stress Scale (PSS), and Center for Epidemiologic Studies Depression Scale (CES-D), with PSS and CES-D reassessed at a 5-week follow-up. Structural equation model was constructed to test mediation pathways with reversed ordering between perceived stress and cognitive vulnerability (Model 1: cognitive vulnerability → perceived stress; Model 2: perceived stress → cognitive vulnerability). Follow-up data were used to examine the stability of these models.</p> Results <p>Cross-sectional results showed that both cognitive vulnerability and perceived stress partially mediated the relationship between childhood trauma and depression, with the direct effect of childhood trauma on depression remaining significant. In Model 1, the dominant pathway was childhood trauma → cognitive vulnerability → perceived stress → depression (55.49% of total indirect effect), whereas in Model 2, the main pathway was childhood trauma → perceived stress → depression (88.99%). Longitudinal data confirmed the stability of both models. Additionally, 30.20% (T1) and 36.82% (T2) of participants exceeded the depression cut-off.</p> Conclusions <p>Childhood trauma contributes to depression via cognitive vulnerability, which amplifies perceived stress. This pathway showed short- term temporal stability, clarifying the directional sequence and highlighting cognitive vulnerability as a key intervention target.</p>