FGF21 and major depressive disorder: The MDD patients presented significantly lower plasma levels of FGF19 and FGF21 than healthy controls as shown in Figure 1 (271.89 ± 146.04 vs. 222.69 ± 108.34, p < 0.05 and 165.17 ± 111.81 vs. 99.84 ± 53.69, p < 0.01).