IGF2 and major depressive disorder: Our group previously reported that the plasma levels of IGF-2 were significantly increased in chronic patients of related psychiatric disorders such as schizophrenia (SZ) (Fernández-Pereira et al., 2022) and major depressive disorder (MDD) (Fernández-Pereira et al., 2023) during either a psychotic or a depressive episode, and those levels were normalized after a period of treatment with antipsychotics or antidepressants, respectively.