NTRK2 and sleep disorder: It has been reported that a large amount of cortisol production induced by hypothalamic‒pituitary‒adrenal axis hyperexcitability is transferred to the central nervous system, leading to apoptosis of neurons in the hippocampal area through activation of the brain-derived neurotrophic growth factor-tropomyosin-related kinase B signaling pathway, which may be a possible mechanism that explains how sleep disorders influence cognitive and behavior dysfunction [25].