Subcallosal Cingulate Deep Brain Stimulation and Heart Rate Variability in Treatment-Resistant Depression: Evidence for Person-Specific Autonomic Phenotypes

Subcallosal cingulate (SCC) deep brain stimulation (DBS) is an established intervention for treatment-resistant depression (TRD) that modulates white-matter tracts within the central autonomic network (CAN). In eight patients with TRD, SCC DBS produced robust antidepressant effects but no group-level change in heart-rate variability (HRV), a marker of vagal flexibility. However, patients whose mood and HRV covaried over time showed greater HRV improvement, suggesting that SCC DBS enhances autonomic flexibility only in individuals with intact mood–vagal coupling.