Introduction
depressive disorder, Depression, MDD
RECURRENCE
Depression is a common chronic and disabling condition that affects an estimated 300 million people worldwide and is associated with personal, societal, and economic burdens.Pharmacotherapy is currently the leading strategy in the treatment of major depressive disorder (MDD).Unlike relapse and recurrence, which occur during the continuation or maintenance phase, loss of a previously effective response while still receiving adequate antidepressant treatment (ADT) occurs in a relatively high proportion of patients with MDD, with rates ranging from 9% to 57%.The causes of FAD remain unclear, and there is a lack of effective treatments.Ketamine, a racemic mixture of 2 enantiomers (esketamine and R-ketamine), is a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist that has been used in clinical practice as a standard anesthetic for nearly half a century.