An impairment of TGF-β1 was observed in animal models of depression with cognitive dysfunction (Yu et al., 2011), whereas a reduction of plasma TGF-β1 levels was detected in depressed patients and correlated with depression symptoms severity and treatment resistance (Myint et al., 2005; Rush et al., 2016; Caraci et al., 2018a). Here, TGFB1 is linked to major depressive disorder.