In this context, the neurotrophic hypothesis of depression posits that MDD is associated with a loss of neurotrophic support, particularly a decrease in BDNF, which leads to neuronal atrophy, reduced synaptogenesis, impaired neurogenesis, and glial loss in key brain regions, such as the hippocampus and dorsolateral prefrontal cortex (DLPFC) [33]. The gene discussed is BDNF; the disease is depressive disorder.