BDNF and major depressive disorder: There were significant correlations between presence of rs6265 in BDNF (P = 0.002) and rs25531 in 5-HTT (P = 0.003) with higher depression scale in group B. Significant correlation between presence of rs6265 in BDNF (P = 0.003), rs25531 in 5-HTT (P = 0.003), rs1800955 in DRD4 (P = 0.003) and rs1611115 in DBH (P = 0.001) with higher depression scale in group D was detected.