BDNF and dementia: Methylation at the BDNF Val66Met site was positively correlated with overall BDNF_IX methylation and methylation at 5 adjacent CpG sites in exon IX but negatively correlated with methylation of BDNF_IV1, BDNF_IV3, and BDNF_I1 amplicons in BDNF promoters I and IV, suggesting the possibility of an indirect effect of BDNF Val66Met polymorphism on dementia and cognition via methylation of BDNF promotor regions.