In this monograph, we briefly review the rationale for deep brain stimulation (DBS) for psychiatric illness, beginning with current noninvasive treatment options and progressing to the evolution and success of DBS as a therapy. This discussion will focus on obsessive-compulsive disorder (OCD) and major depressive disorder (MDD) particularly, as these are the only two diagnoses that have been subjected to adequately controlled DBS trials to date. The majority of the essay then describes the significant limitations that DBS is currently facing and emerging approaches to address them. This will lead into a discussion of new technologies such as patient-specific modeling of electric fields and closed-loop DBS systems and how we can best utilize these to increase our understanding of DBS and the overall efficacy of this novel therapy.