Prognostic: To classify MDD severity Therapeutic: Animal models show: an inhibitor may block neuronal apoptosis activating Notch 1 signaling pathway, which is key for neural development and brain homeostasis (neuronal connectivity, synaptic plasticity and learning/memory). Notch signaling pathway is crucial in early neurodevelopment and late-life neurodegeneration. Here, NOTCH1 is linked to major depressive disorder.