Treatment-resistant Depression (TRD) is the failure of pharmacological treatment, with or without psychotherapy or electroconvulsive therapy, in major depressive disorder patients. Over the past years, various trials of Deep Brain Stimulation (DBS) in TRD patients have been performed. By means of a systematic Pubmed search, the reports on these trials were gathered and critically appraised. Even though the reported research methodology was flawed, the combined study outcomes (of a total of fifty patients, 58% (95% CI = [44.2%; 70.6%]) showed a response to treatment and 26% (95% CI = [15.8% ; 39.7]) were considered being in remission) are promising. Nonetheless, further research is required to evaluate the most beneficial stimulation areas in the brain, the stimulation parameters, and the possible long-term therapeutic and side-effects.