The neural substrates of different depression symptoms: Animal and human studies

In this chapter, we discuss psychological and neural data related to the different symptoms of major depressive disorder (MDD), including low mood, psychomotor retardation, anhedonia and cognitive impairment among others. Here, we discuss both animal and human experimental studies to show that MDD symptoms are related to alterations to different molecular, cellular, and system-level mechanisms of the brain. We further discuss how antidepressants ameliorate these symptoms and impact different structural and neurochemical systems. We here argue that most symptoms of depression cannot be deduced to a single biological factor.