NMDA Modulation in Antidepressant Nonresponders With Major Depressive Disorder

Major depressive disorder (MDD) is a multi-factorial disorder. Most of the current antidepressants are based upon the monoamine hypothesis which cannot fully explain the etiology of depression. Many patients respond poorly to antidepressants and suffer from side effects. NMDA hypofunction has been implicated in the pathophysiology of depression. MDD is often associated with cognitive deficits which are not necessarily recovered by current antidepressants. The NMDA receptor regulates synaptic plasticity, memory, and cognition. Therefore, this study aims to examine the efficacy and safety as well as cognitive function improvement of NMDAE in the treatment of antidepressant nonresponders with MDD. The investigators will enroll a total of 50 antidepressant nonresponders with MDD. All patients, continuing their originally ongoing treatment throughout the study period, will be randomly assigned into either of two treatment groups: NMDAE or placebo. We will biweekly measure clinical performances using 17-item Hamilton Rating Scale for Depression, Global Assessment of Function, Perceived Stress Scale, Visual Analogue Scale for pain, Clinical Global Impression, and side effects. Quality of life and cognitive functions will be assessed at baseline and at endpoint of treatment. The efficacies of NMDAE and placebo will be compared. Chi-square (or Fisher's exact test) will be used to compare differences of categorical variables and t-test (or Mann-Whitney test if the distribution is not normal) for continuous variables between treatment groups. Mean changes from baseline in repeated-measure assessments will be assessed using the generalized estimating equation (GEE). All p values for clinical measures will be based on two-tailed tests with a significance level of 0.05.