Neuroanatomical Substrates of emotional Dysregulation in Bulimia Nervosa

Objective We aimed to elucidate the neuroanatomical alterations in drug-free young females with BN and their relationship to core illness severity and comorbid emotional symptoms. Methods A total of 53 adult female patients with BN and 52 age- and sex- matched healthy controls (HCs) were included in the study and underwent high-resolution T1-weighted MRI scans. We applied both voxel-based morphometry (VBM) and surface-based morphometry (SBM) methods to comprehensively explore gray matter (GM) alterations in BN patients. Correlations and mediation analyses were further performed to assess the relationships among morphological alterations, depression or anxiety symptoms and eating disorder symptoms in BN patients. Results Compared to HCs, BN patients exhibited reduced GMV/CV in the bilateral lingual and calcarine gyri, right superior temporal gyrus, and bilateral posterior cerebellum. Among these regions, the right lingual gyrus volume correlated negatively with shape concern scores for eating disorder, while bilateral posterior cerebellar volumes correlated negatively with depression and anxiety symptoms. We also found that depression and anxiety symptoms fully mediated the association between left posterior cerebellar volume and eating disorder severity, with depression demonstrating a significantly stronger mediating effect than anxiety. Conclusions Our study identifies convergent gray matter reductions in cerebellar, occipital, and temporal regions in BN. Notably, we demonstrated that comorbid depression and anxiety symptoms fully mediate the link between posterior cerebellar volume and eating disorder severity. Our finding emphasized the cerebellum as a neurobiological locus where emotional dysregulation converges to exacerbate BN, offering a novel target for pathophysiology-informed treatment strategies.