BDNF and sleep disorder: Existing studies have reported that sleep problems such as sleep deprivation and sleep disorder can increase oxidative stress response in the prefrontal cortex, hippocampus, and amygdala, reduce cells in the prefrontal cortex and amygdala, and decrease the volume of the hippocampus, resulting in a low level of neurotrophic activity and reduced expression of brain-derived neurotrophic factor (BDNF), thus increasing negative emotions [43,44,45].