Neural mechanisms of rumination subtypes in adolescent major depressive disorder based on large-scale brain network analysis

INTRODUCTION: The incidence of adolescent major depressive disorder (MDD) is rising. Rumination, a core cognitive factor in its onset and maintenance, divides into adaptive reflective and maladaptive brooding subtypes. Brooding exacerbates symptoms and predicts future episodes, suggesting distinct neural bases. Given adolescents' critical brain development, exploring brain network-rumination subtype links deepens MDD neural understanding and informs subtype-specific interventions. This study uses resting-state EEG to investigate large-scale network characteristics in adolescent MDD and their specific associations with reflection and brooding. METHODS: The study included 121 first-episode, medication-naive adolescent MDD patients and 99 healthy controls (HC). Resting-state EEG, Hamilton Depression/Anxiety Scale (HAMD/HAMA), and Ruminative Responses Scale (RRS) data were collected. Phase synchronization analysis examined functional connectivity differences within/between DMN, SN, FPN across Delta, Theta, Alpha, Beta, Gamma bands. Correlations with reflection and brooding were analyzed. RESULTS: Compared with HC, MDD showed widespread enhanced connectivity within/between DMN, SN, FPN across multiple bands. Brooding negatively correlated with Alpha-band DMN-SN (PCG.R-ACG.L) and Gamma-band FPN-SN (IPL.R-AMYG.R) connectivity. Reflection positively correlated only with Beta-band FPN-SN (IPL.R-ACG.L) connectivity. Sensitivity analysis in the 14-23-year-old subgroup confirmed the robustness of core findings: the differentiated associations between rumination subtypes and specific network patterns remained consistent. CONCLUSION: Adolescent MDD exhibits abnormal enhancement of large-scale brain network connectivity across bands, with distinct rumination subtypes showing differentiated associations with specific network patterns. These findings provide electrophysiological evidence for understanding rumination mechanisms in adolescent depression and potential targets for personalized neuromodulation.