On the other hand, other studies did not show different serum levels of BDNF in MDD patients compared with controls (Duman et al., 1997), and others also described an improvement in BDNF levels in women but not in men after antidepressant treatment (Huang and Hung, 2009; Polyakova et al., 2015b; Martinotti et al., 2016; Lin et al., 2017). The gene discussed is BDNF; the disease is major depressive disorder.