According to the neurotrophic hypothesis of depression, the deficiency of BDNF and other growth factors may contribute to the atrophy of certain limbic structures, including the hippocampus and prefrontal cortex, observed in patients with depression, and antidepressant drugs act by increasing the levels of BDNF [18,19,20,21,22,23]. The gene discussed is BDNF; the disease is depressive symptom measurement.