GSTM1 and major depressive disorder: Regarding the blood tests, the risk of depression was increased by 0.4% (OR = 1.004, 95%CI = 1.001–1.007) for every unit increase in PTH, but it decreased by 4% for each unit increase in Hb (OR = 0.960, 95% CI = 0.926–0.996) in the MHD patients.