Deep brain stimulation for the treatment of major depressive disorder: complex psychiatric aspects

Dear Editor,
The fascinating review article on brain stimulation for treatment-resistant depression published by Michał Sobstyl and Angelika Stapińska-Syniec [1] raises many questions. In the following pages these questions are addressed, and commentary offered, on the application of deep brain stimulation (DBS) in major depressive disorder (MDD).
As the authors correctly stated, the issue is significant because, on average, 30% of individuals with MDD are classified as treatment resistant (TRD) [2, 3]. Usually, TRD is defined as two sufficient antidepressant trials that have failed to produce an “adequate response” [3, 4]. However, there is a lack of wide consensus as to this definition of TRD [5]. For instance, the biological process underlying the TRD is not entirely understood. All of these factors could result in disagreements over patient enrollment in DBS treatment [4]. Nevertheless, most of the relevant TRD algorithms rank DBS as the last-line treatment [3]. When both pharmacological and non-pharmacological approaches (including interventional ones, such as electroconvulsive therapy) augmented with psychotherapy have failed, DBS may be considered. The number of available treatment methods is constantly growing due to the introduction of new biological techniques; recently we have seen the emergence of esketamine and transcranial direct current stimulation [3, 4].
Furthermore, there are a variety reasons that could cause pseudo-resistance to treatment in MDD. Examples include factors related to the treatment itself (e.g. inadequate doses, too-short treatment times, the patient’s non-adherence), comorbidity (e.g. personality disorders), misdiagnosis (e.g. depressive episode in bipolar disorder) or individual or social factors (e.g. entering the role of patient, unconscious need to be subject of care), to name just a few [5]. There are currently no definite clinical recommendations that would specify which patient subgroups would particularly benefit more from DBS treatment and perhaps should have been offered this approach sooner. However, because it is the most invasive treatment option for psychiatric disorders, the conditions of each patient should be carefully considered.
Some questions about DBS still remain open – placebo effect is one of them. Although it has been suggested that they are insignificant in individuals who are severely depressed, placebo rates are often very high in clinical trials for depression...


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