Similarly, Yang et al. (2024) found that vitamin D injections (400–1600 IU/week/mouse) significantly improved depression-like behaviors in adolescent mice subjected to Unpredictable Chronic Mild Stress (UCMS), despite no significant increase in hippocampal BDNF expression (p > 0.05) [30]. The gene discussed is BDNF; the disease is major depressive disorder.