Brain‐derived neurotrophic factor (BDNF), one of the neurotrophic factors, does main favour in neurogenesis, neural survival and growth.40, 41 BDNF binds to its tropomyosin receptor kinase B (TrkB) to activate downstream signalling pathways and then completes phosphorylation and activation of the cAMP response element‐binding protein (CREB).42 The BDNF reduction in both hippocampus and PFC is closely associated with depression. Here, BDNF is linked to depressive symptom measurement.