In addition, preclinical and clinical evidence suggest that patients with depression tend to present lower levels of serum BDNF when compared to healthy individuals (Wilkinson et al., 2018; Ma et al., 2019), which may be reversed after antidepressant drug treatment (Brunoni et al., 2017; Molendijk et al., 2018). The gene discussed is BDNF; the disease is major depressive disorder.