BDNF and depressive disorder: The BDNF precursor proBDNF was found to be able to induce cell apoptosis in cultured neurons [58], AD cases [59], and post-stroke depression cases [60] through the interaction with the P75NTR receptor and its co-receptor sortilin; however, it still remains unclear whether proBDNFVal carriers are at higher risk than proBDNFMet carriers, making more research on this topic necessary.