Recently, Shi et al. performed a comprehensive meta-analysis on the blood neurotrophins for the clinical application of MDD and revealed that significantly reduced brain-derived neurotrophic factor (BDNF) and significantly increased insulin-like growth factor-1 (IGF-1), vascular endothelial growth factor (VEGF), and S100B protein may be potential diagnostic biomarkers for MDD (14). This evidence concerns the gene BDNF and major depressive disorder.