**5. Conclusions**

More personalized treatment approaches hold the potential to increase the overall efficacy of DBS for TRD. Precise evaluations of symptoms, biomarkers, and resting-state connectivity patterns are essential when distinguishing clinical subtypes of TRD. Moreover, subtyping may provide more insight into the working mechanisms of DBS and help in selecting optimal targets in patients. Monitoring of biomarkers at multiple time points during treatment along with evaluation of ESM data, in parallel with clinical assessments of mood using standardized depression-rating scales, will lead to a better understanding of symptom changes when stimulating specific brain regions. Such considerations could further lead to optimal adjustments of stimulation parameters as long-term effects of DBS on mood occur.

**Author Contributions:** M.R. and E.S. prepared the first draft. J.B., A.E.P.M., A.F.G.L. and A.J. provided inputs and revised the manuscript. A.J. supervised the process. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
