After gender grouping, there was a significant positive correlation between proBDNF and HAMD-17 scores in male MDD patients (ρ=0.400, p<0.05), a negative correlation between BDNF levels and HAMD-17 scores in female MDD patients (ρ=-0.261, p<0.05), and IL-18 levels and HAMD-18 scores in female MDD patients were negatively correlated (ρ=-0.244, p<0.05) (Figure 2). The gene discussed is BDNF; the disease is major depressive disorder.