Neurotrophic factors, particularly the brain-derived neurotrophic factor (BDNF), have important roles in the pathophysiology of depression and in the therapeutic effects of antidepressant treatment (Duman and Monteggia, 2006; Castrén and Rantamäki, 2010; Hashimoto, 2015). This evidence concerns the gene BDNF and depressive symptom measurement.