The Efficacy and Prediction of Deep Brain Stimulation for Treatment-resistant Depression

Major Depressive Disorder (MDD) is a highly prevalent psychiatric disorder, with an estimated lifetime prevalence of 14.6% across high-income countries.Effective therapeutic options for MDD include psychotherapy, different classes of antidepressants, and electroconvulsive therapy (ECT). Nevertheless, up to 30% of patients do not respond to four consecutive antidepressant strategies and 52% of pharmacotherapy resistant patients do not respond to ECT.Such patients are designated an advanced stage of Treatment Resistant Depression (TRD), which is associated with more hospitalizations, more suicide attempts, and higher costs than non-TRD patients. Deep Brain Stimulation (DBS) is a promising therapeutic option for TRD patients. DBS consists of implanting electrodes in specific brain areas and then optimizing stimulation parameters (e.g. voltage, frequency, pulse width) to modulate brain activity of the targeted area. Since 2005, several open label trials have reported promising effects of DBS in TRD, targeting different brain structures involved in the neurobiology of MDD: the Subcallosal Cingulate Gyrus (SCG),Medial Forebrain Bundle (MFB),Ventral Capsule/Ventral Striatum (VC/VS), and Nucleus Accumbens (NAc). Response rates, defined as a symptom decrease of at least 50%, range from 30% to 90% with most studies finding a response rate around 50%. However, results of the first two randomized trials are mixed. The first randomized, controlled trial (RCT) of VC/VS DBS in TRD did not find differences in response rates following active (3 of 14 patients) or sham stimulation (2 of 15 patients) after four months of stimulation. In contrast, another group found a strong antidepressant effect in 16 patients with TRD following active ventral Anterior Limb of the Internal Capsule (vALIC) DBS compared to sham stimulation in a randomized crossover phase. Therefore, this trial aims to establishing whether active DBS results in more treatment responders than sham DBS. Secondary aims are establishing an adverse events profile, establishing effects on quality of life,neuropsychological and neuroimaging measures, and finding predictors of response.