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 Here, BDNF is linked to depressive symptom measurement.