BDNF as a biomarker in diagnosis and evaluation of treatment for schizophrenia and depression.

Schizophrenia and major depression disorders, both being of pathological synaptogenesis, are the most common psychiatric disorders worldwide. These diseases, if not treated effectively, may cause suicide and are a serious social and economic challenge. Although schizophrenia and depression can be significantly improved with the second-generation atypical antipsychotics, rising drug resistance has limited their efficacy. Repetitive Transcranial Magnetic Stimulation (rTMS) has appeared to be a promising therapy against severe mental disorders, but it is still controversial primarily due to inadequate evaluation. It is essential to have a reliable biological marker to evaluate and diagnose schizophrenia or depression. Brain-derived neurotrophic factor (BDNF) has appeared to play a critical role in certain neurobiological modifications that may otherwise lead to schizophrenia or depression. Meta-analyses have demonstrated that serum BDNF levels were tightly correlated with the courses of severe schizophrenia and major depression disorders. This article presents a review of BDNF as a neurobiological marker for schizophrenia and depression and for the efficacy of rTMS treatments of these mental diseases.