The neurotrophic hypothesis of MDD posits that reduced neurotrophic factors, especially brain-derived neurotrophic factor (BDNF) and VEGF, can induce neuronal atrophy in brain regions associated with MDD, an important mechanism underlying depressive symptoms (Duman et al., 2016; Rana et al., 2021; Uslu and Yildiz, 2024). The gene discussed is BDNF; the disease is major depressive disorder.