GSK3B and major depressive disorder: For GSK3β polymorphisms, individuals with an A-allele had a higher risk of developing MDD than those who carried a G-allele at GSK3β gene SNP site rs334558/rs6438552, and individuals with a G-allele had a higher risk of developing MDD than those who carried an A-allele at GSK3β gene SNP site rs2199503.