In short, new evidence shows that proBDNF and mature BDNF elicit opposing effects via the p75NTR and TrkB receptors, respectively, and that both proBDNF and mature BDNF play important roles in several physiological functions of neurons, which might be related to the pathology of psychiatric disorders such as mood disorders and schizophrenia [5–9]. This evidence concerns the gene BDNF and psychiatric disorder.