In one study, a meta-analysis implicated the Val66Met polymorphism in trauma-exposed individuals with PTSD.98 Researchers have reported that in veterans with PTSD, when compared to veterans without PTSD, peripheral BDNF protein levels were lower, and DNA methylation in the gene promoter was higher.99 For the BDNF gene, alcohol appears to compensate for ELS- or PTSD-induced deficiencies, as demonstrated by a study in which acute alcohol administration led to histone acetylation-associated increases in the central and medial amygdala of alcohol-preferring rats.100. Here, BDNF is linked to post-traumatic stress disorder.