Neuroanatomical landscapes: Delineating the cortical signatures of pediatric major depressive disorder and bipolar disorder

Pediatric mood disorders, including Major Depressive Disorder (MDD) and Bipolar Disorder (BD), exhibit overlapping symptomatology and complex neurodevelopmental trajectories, necessitating a comprehensive investigation of their neuroanatomical underpinnings. This study aimed to characterize structural brain differences in children with MDD and euthymic BD using high-resolution structural magnetic resonance imaging (MRI). A total of 51 children (aged 10-14 years) were categorized into MDD, euthymic BD, and typically developing (TD) controls. Utilizing advanced surface-based morphometry, we examined four cortical features: fractal dimension, gyrification, sulcal depth, and cortical thickness, to delineate disorder-specific and shared neuroanatomical alterations. Additionally, we explored the interaction between white matter volumetrics and these surface-based metrics to assess its modulatory role in structural brain differences. Our results revealed significant cortical alterations, with distinct and overlapping patterns in both MDD and BD. The findings demonstrated disruptions in cortical complexity, folding patterns, and sulcal morphology, particularly in regions implicated in emotion regulation and cognitive processing. These structural variations provide critical insights into the neurodevelopmental alterations associated with pediatric mood disorders. By integrating multiple morphometric parameters, this study offers a comprehensive framework for understanding the neuroanatomical changes in MDD and BD, contributing to more precise diagnostic biomarkers. The results underscore the importance of incorporating surface-based morphometry and white matter interactions in future research to refine early diagnosis and targeted interventions for mood disorders in children.