Objective: To replicate previous findings and to investigate related clinical factors of long-term benefits and safety of subcallosal cingulate gyrus deep brain stimulation (SCG-DBS) for treatment-resistant depression (TRD).Methods: Sixteen patients with TRD (with either major depressive disorder or bipolar disorder, DSM-IV and DSM-5 criteria) receiving chronic SCG-DBS were followed for up to 11 years (January 2008 to June 2019). Demographic, clinical, and functioning data were collected pre-surgery and during the follow-up. Response was defined as a ≥ 50% decrease from baseline in the 17-item Hamilton Depression Rating Scale (HAM-D17) score, and remission was defined as ≤ 7 in the HAM-D17 score. The Illness Density Index (IDI) was used as a longitudinal measure of treatment effects. Survival analyses were performed for response outcomes and relapses.Results: Depressive symptoms were significantly decreased over time (F = 2.37; P = .04). Response and remission rates were 75% and 62.5% at individual endpoint. Based on Kaplan-Meier curve analysis, 55% of patients reached remission in 139 days. IDI curves showed sustained clinical improvements as measured with HAM-D17 and Clinical Global Impression and sustained functioning improvement as measured with Global Assessment of Functioning scores. The procedure was generally safe and well tolerated (122 adverse events across 81 patient-years, of which 25 were related to SCG-DBS). Two patients committed suicide long after surgery.Conclusions: SCG-DBS produced a robust and protracted improvement in most patients, which reinforces the possibility that SCG-DBS could be an alternative for patients with treatment-resistant unipolar or bipolar depression. Identification of clinical and neurobiological response predictors should guide the continuation of DBS for TRD, to obtain its indication soon.