Also, stress can suppress BDNF expression (58), and decreased BDNF expression has been shown to be associated with epigenetic modification of the BDNF gene (59), as well as depressive disorder and other mental disorders in late life (22, 60, 61), which eventually leads to our primary interest whether BDNF methylation play a role in mediating early life adversities and mental health issues in adults over 65 years of age. This evidence concerns the gene BDNF and depressive disorder.