Fortunately, tranylcypromine a drug developed decades ago and FDA approved for the treatment of depression and anxiety (Burger and Yost, 1948) has recently been shown to irreversibly inhibit LSD1 as a side effect (Binda et al., 2010; Ulrich et al., 2017; Zheng et al., 2016). This evidence concerns the gene KDM1A and major depressive disorder.