TGFB1 and major depressive disorder: Clinical observations have shown that TGF-β1 levels are inversely correlated with the severity of depressive symptoms (61), and a resurgence of TGF-β1 levels can be observed after treatment with some antidepressants (36, 62), suggesting that TGF-β1 may not only participate in the pathophysiological process of depression but also serve as a potential biomarker of treatment response.