In recent years, there has been growing evidence to show that the brain-derived neurotrophic factor (BDNF)/TrKB pathway can modulate serotonin (5-hydroxytryptamine; 5-HT) and other neurotransmitters, and this pathway has been implicated in the pathophysiology and treatment of depression and anxiety (14). This evidence concerns the gene NTRK2 and depressive symptom measurement.