BDNF and major depressive disorder: A meta-analysis found no differences in the decrease of peripheral BDNF levels among patients with mood disorders (major depression, bipolar depression and manic episode) and schizophrenia in acute states.11 In addition, decreased BDNF levels were observed in mood disorders during acute episodes when compared with those levels in euthymia/remission.11 Because most studies have shown a decrease in BDNF9, 12 in schizophrenia, BDNF can be considered a schizophrenia biomarker, and may also have a role in the process of neuroprogression in other neuropsychiatric disorders.13