BDNF and depressive disorder: The neurobiological mechanisms that could explain the association between depression and diabetes mellitus type 228 could include 1) the alterations involved in the metabolism of biogenic amines (serotonin and norepinephrine), from the adrenal-pituitary-hypothalamus axis (by increasing cortisol)28–30; 2) trophic agents such as Brain Derived Neurotrophic Factor (BDNF) through Glycogen Synthase Kinase-3 (GSK-3)31,32.