PON1 and major depressive disorder: Significant reductions in reverse cholesterol transport (RCT) (mainly lower HDL cholesterol and paraoxonase 1) and increases in lipid peroxidation and aldehyde formation were found in patients with MDD and bipolar disorder (BD) compared to healthy controls [16], indicating that the lowering of RCT is a critical antioxidant and anti-inflammatory route in MDD/BD [17,18].