BDNF and major depressive disorder: Promoter hypermethylation generally leads to reduced gene expression.39 Our finding of elevated BDNF promoter methylation associated with depression strongly supports observations of reduced BDNF levels in the plasma and post-mortem hippocampus of depressed individuals.7, 8, 39, 40 Decreased BDNF may relate to the reduced function of BDNF gene in promoting neural growth and repair in depression.41