[Treatment resistant depression: actuality and perspectives in 2017].

Major depressive disorder (MDD) affects 3 to 17 % of adults. 15 to 30 % of patients with MDD suffer from treatment resistant depression (TRD). No international consensus defines TRD. The most common definition is " MDD that is not enough improved after two successive and different classes of antidepressant treatments in appropriate dose and duration ". The appropriate dose corresponds to maximal dose accepted by scientific reports and clinical recommendations, while the appropriate duration is around 6 weeks. TRD is diagnosed after excluding a pseudoresistant depression, that is related to weak compliance or to somatic and psychiatric differential diagnosis. As well as in MDD, molecular, neuro-anatomical and metabolic disturbances are involved in TRD. A decreased cerebral plasticity induced by low level of Brain-Derived Neurotrophic Factor (BDNF) is also reported. Several authors describe that the cerebral atrophy and the dopaminoglutaminergic system disturbances are more severe in TRD than in MDD. In contrast to MDD treatment, TRD treatment is most often physical treatment. Electroconvulsive therapy (ECT) followed by a tricyclic antidepressant and/or lithium is the most effective treatment. Deep brain stimulation and vagal nerve stimulation reach also a high rate of remission but they are both very invasive technique. Repetitive transcranial magnetic stimulation in TRD seems to be effective in TRD but lower than ECT. There are two majors purposes for this review. First it may help the clinician to understand the TRD's complexity and also it details the kind of treatment useful to care it.