BDNF and depressive disorder: In addition, another study found that prenatal stress could inhibit the proteolytic conversion of proBDNF to the BDNF in the rat hippocampus.26 Interestingly, we report for the first time that the decreased serum BDNF/proBDNF ratio in depression was reversed by antidepressant treatment, suggesting that the antidepressant effect might be due to the elevation of the BDNF/proBDNF ratio.