Thus, (1) having adverse childhood experiences is related to MDD during adult life; (2) the combination between MAO-A and MAO-B gene variants may ameliorate to a certain level the association of adverse childhood experiences [1] and depression; (3) adding interactive terms that are associated to higher correlations with the HDRS total score, implied a better model of depression severity; and (4) both genetic factors and temperamental traits could ameliorate the impact of adverse childhood experiences in the development of MDD in adulthood. The gene discussed is MAOA; the disease is major depressive disorder.