Although the mechanisms linking sports practices to decrease depressive symptoms are still unclear [57], some biological evidence links neuromuscular mechanisms, namely increased expression of neurotrophic factors (i.e., BDNF) [58], increased serotonin and norepinephrine availability [59], regulation of HPA-axis activity [60], and decrease systemic inflammatory signaling [61], to mood and depression. The gene discussed is BDNF; the disease is major depressive disorder.