Shao et al. found the CSF miR-16, which has been suggested to be a biomarker for anxiety49, has a role in the pathogenesis of depression via affecting raphe SERT expression50, and play a role in the development of depressive-like behaviors in the hippocampus by targeting and downregulating BNDF expression51 via PI3K/Akt/mTOR pathway52. This evidence concerns the gene SLC6A4 and major depressive disorder.