Chen et al. 2011 measured BDNF exon IV expression and H3K27 trimethylation levels in post-mortem prefrontal cortex of MDD patients who had completed suicide with a history of, and toxicology positive for, antidepressants (n = 7), MDD subjects who completed suicide with no history of antidepressant use and negative antidepressant toxicology (n = 11), and control subjects with no psychiatric history (n = 9) [58]. Here, BDNF is linked to major depressive disorder.