“…The monoamine theory, which has been the most widely accepted over recent decades, ascribed depression to an insufficient amount of serotonin and norepinephrine in the synapses located in the dorsal raphe nuclei and locus coeruleus, respectively. Serotonin neurotransmission is crucial in contributing to several important brain functions that are responsible for regulating mood, fear response, sleep, appetite and sexual behavior (Pierz & Thase, ). Norepinephrine signaling plays a vital role in coordinating neuronal network excitability and connectivity, as well as modulating behavior response and adaptation, while its deficiency leads to decreased alertness, low energy, stress, working memory impairment and problems in attention, concentration, motivation and cognition (Moret & Briley, ; O'Donnell, Zeppenfeld, McConnell, Pena, & Nedergaard, ).…”