Repetitive Negative Thinking and Somatic Symptoms as Mediators of the Relationship between Childhood Abuse and Depression Severity in Major Depressive Disorder

Objective: Major depressive disorder (MDD) is highly heterogeneous, and adverse childhood experiences (ACEs) contribute significantly to its variability. While abuse-type ACEs are linked to worse outcomes, the specific mechanisms remain poorly understood. This study tests a novel model in which abuse-specific ACEs, compared to neglect or household dysfunction, exert a stronger influence on depression severity by increasing repetitive negative thinking (RNT), which in turn amplifies somatic symptom burden. Method: In a cross-sectional study, 435 adults with a confirmed DSM-5 diagnosis of MDD were recruited from psychiatric clinics. Participants completed the Childhood Trauma Questionnaire (CTQ), the RNT Questionnaire (RNTQ), the Patient Health Questionnaire-15 (PHQ-15) for somatic symptoms, and the Beck Depression Inventory-II (BDI-II). Using structural equation modeling (SEM), we tested a dual mediation model where abuse, neglect, and household dysfunction ACEs predicted BDI-II scores via direct and indirect pathways, with a focus on the sequential path through RNT and somatic symptoms. Results: The model demonstrated excellent fit (CFI = 0.96, RMSEA = 0.04) and accounted for 54% of the variance in depression severity (R² = 0.54). Abuse ACEs had a significantly stronger total effect on depression severity than other ACE types (β = 0.41 versus ≤ 0.18, P < 0.01) and also exerted a significant direct effect on depression severity (β = 0.22, P = 0.012). The specific indirect pathway from abuse ACEs to RNT to somatic symptoms to depression was also significant (β = 0.19, 95% CI [0.13, 0.26]), accounting for 46% of the total effect of abuse on depression (total effect β = 0.41, P < 0.001). This pathway was significantly stronger (P < 0.001) than analogous pathways from neglect or household dysfunction ACEs. Conclusion: The path from childhood abuse to severe depression is characterized by a cognitive-somatic cascade: abuse fuels persistent negative thinking, which exacerbates the perception and burden of physical symptoms, ultimately deepening depressive severity. This identifies a specific phenotypic profile (high RNT + high somatic burden) associated with abuse histories, highlighting essential targets for tailored intervention in trauma-informed depression care.

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