ABSTRACT
Major depression is one of the world’s leading causes of morbidity and mortality. It affects approximately 14.8 million American adults, or about 6.7% of the U.S. population age 18 and older, in a given year.1 Depression can either be chronic or recurrent, and symptoms can be quite heterogeneous with both psychological and physical manifestations. Treatment-resistant depression (TRD), is dened as a failure of two or more medication trials with antidepressants from different pharmacologic classes that fail to produce a signicant clinical improvement. TRD is often the norm, not the exception, in the course of treatment for major depression. A multicenter study involving over 2876 patients, referred to as Star-D, revealed that approximately 50% or more of patients with major depression remain refractory to treatment, even after all four treatment levels.2
