Depression is one of the most prevalent mental disorders around the world. The patho mechanism of major depressive disorder has expanded beyond the scope of the monoamine hypothesis. Due to it's multi complex features, no single theory has proven enough to explain both the polymorphic nature and the identification of biomarkers that can be reliably used for the diagnosis of depression. As a result, modern behavioral accounts of major depressive disorder must look at both interoceptive and environmental components. Pharmacotherapy of depression include the use of selective serotonin reuptake inhibitors (SSRIs) and serotonin norepinephrine reuptake inhibitors (SNRIs). Antidepressant treatment regimen has various side effects, including drug tolerance, delayed response and unsatisfactory efficacy. Besides, antidepressant non-responsiveness rates range from 30 to 50%. Therefore, finding Besides, Novel drug therapies for a better treatment of depressive disorders particularly for treatment of resistant depression (TRD) have been proven. Other modalities such as electroconvulsive therapy (ECT) can also be used predominantly for the treatment of suicidal and severe cases of depression.