APOE and major depressive disorder: APOE ε4 allele was significantly associated with depression (allele: OR=1.36, 95%CI=1.11-1.66, P=0.003; dominant: OR=1.34, 95%CI=1.06-1.68, P=0.001; recessive: OR= 1.11, 95%CI =0.45-2.76, P=0.82).