Treatment-resistant depression (TRD) is diagnosed after an individual has tried several types of treatment for depression and their symptoms haven’t improved. The effectiveness of deep brain stimulation (DBS) as a treatment for disorders such as Parkinson’s disease has led researchers to investigate whether it could also work for psychiatric disorders such as TRD. However, depression varies significantly among individuals, and studies on DBS for TRD have also produced variable results. This points to a need to personalize DBS treatment for individuals with depression.