In addition, miRNA and circRNA can restore their abnormal functions in depression by regulating specific signals, which may imply the impairment of genes implicated in pathways of MDD etiopathogenesis, such as neuroinflammation, brain-derived neurotrophic factor (BDNF), neurotransmitters, hypothalamic–pituitary–adrenal (HPA) axis, PI3K/Akt signal, and et al. [14]. This evidence concerns the gene BDNF and major depressive disorder.