Carrying the ε3/4 genotype of the APOE gene increased the odds of developing major depression by 2.167 times (95%CI 1.100–4.266) compared to carrying the ε3/3 genotype of the APOE gene in people without depression (χ2 = 5.120 df = 1 p = 0.024). Here, APOE is linked to major depressive disorder.