Several studies have also demonstrated that a decrease in the levels of neurotrophic factors (NTFs), such as brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF), is associated with the pathology of neurodegenerative diseases [15,16,17,18,19,20] and that this decrease is closely linked to neuronal cell death [21,22]. Here, BDNF is linked to neurodegenerative disease.