Occipital structure is linked to vagal tone in borderline personality but not in major depressive disorder.

Major depressive (MDD) and borderline personality disorders (BPD) are highly prevalent and frequently comorbid psychiatric conditions, both characterized by emotion dysregulation yet likely arising from distinct etiologies. Nonetheless, the specific features of autonomic central-peripheral relationships in these disorders remain poorly understood. We investigated the association between brain structure and vagal activity, and explored the resting-state functional connectivity of brain regions found to be associated with vagal tone, in 19 MDD, 18 BPD and 20 healthy controls (HC). We found that the cortical thinning in the right lateral occipital region was associated with increased parasympathetic tone in BPD, a relationship not observed in MDD. Moreover, in BPD, this region was functionally connected to the anterior insula and prefrontal areas, linked to the central autonomic system and emotion regulation processes. Accordingly, this region was also linked to emotion dysregulation in BPD. Our findings highlight distinct central-peripheral autonomic integration in these disorders and emphasize the occipital region's structural and functional involvement in emotional and autonomic regulation in BPD. Further research is needed to clarify how occipital structure and function, well as vagal activity, may contribute as potential biomarkers for BPD.