IL-10 is a key regulator of depression symptoms and modulates depressive-like behaviour.[14] IL-10 knockout mice display increased depressive-like behaviour compared with the wild type and this is converted by injection of IL-10.[15] Therefore, the effect of clomipramine on the serum levels of this cytokine may contribute to its therapeutic effect in major depressive disorders. This evidence concerns the gene IL10 and major depressive disorder.