MMP9 and major depressive disorder: The Zhigancao decoction group exhibited significantly higher efficacy rates, improved left ventricular ejection fraction (LVEF), reduced levels of inflammatory markers [N-terminal pro-brain natriuretic peptide (NT-proBNP), matrix metalloproteinase-9 (MMP-9), and high-sensitivity C-reactive protein (hs-CRP)], and lower scores on depression scales, compared to the control group.