In a naturalistic study of 108 patients with MDD, Kang et al. 2013 measured PBMC BDNF promoter methylation and suicidal ideation (SI) severity over a twelve week treatment period with one of nine antidepressants (amitriptyline, bupropion, escitalopram, fluoxetine, imipramine, mirtazapine, paroxetine, sertraline, and venlafaxine) chosen clinically [54]. Here, BDNF is linked to major depressive disorder.