Several cross-sectional studies suggest that BDNF was a trait marker for depression and correlated with neuroticism.30, 31, 32, 33, 34 In contrast, the first cohort study36 did not necessarily show lower BDNF levels in an incident MDD group at baseline, although the study did not eliminate the effects of MDE history. The gene discussed is BDNF; the disease is major depressive disorder.