BDNF and major depressive disorder: The bilateral comorbidity of thesedisorders (depression aggravates the course of diabetes and vice versa) hasbeen studied [22, 23].In addition to the convincing data on the role of adeficiency in the brain-derived neurotrophic factor (BDNF) in the pathogenesisof depressive states of different etiologies, including in patients withdiabetes [24], it has been demonstratedthat the activity of NGF drops both in depression and in diabetes, which isconsidered to be an important factor that determines their comorbidity.