Major depressive disorder (MDD) is a heterogeneious psychiatric disorder with complex etiology and pathogenesis. The lack of objective criteria for diagnosis and the use of trial-and-error treatment strategy are the current challenge. Anhedonia is the core symptom of MDD and the aberrant reward system and abnormal inflammatory immune may be the pathological mechanisms. Previous evidence suggests anhedonia cannot be improved quickly and efficiently by taking the first-line antidepressants. This study focuses on exploring the optimal diagnosis and treatment strategy for MDD patients with anhedonia. Based on the hypothesis of inflammatory-immune system，neurotransmitter abnormalities and aberrant reward system, this study aims to evaluate the efficacy and safety of the combinations of escitalopram and aripiprazole and/or omega-3 polyunsaturated fatty acids for MDD patients with anhedonia with a factorial design. Moreover, the multidimensional data including the clinicopathological features, neuroimaging data (MRI) and inflammatory cytokines will be used to establish the model of diagnosis and treatment strategy.
