Alterations of serum levels of brain-derived neurotrophic factor (BDNF) in depressed patients with or without antidepressants

Background Because researchers have reported that antidepressants increase the expression of brain-derived neurotrophic factor (BDNF) in the rat hippocampus, we investigated whether serum BDNF levels may be used as a putative biological marker for major depressive disorders (MDD). Methods We measured serum BDNF in the following three groups: antidepressant-naive patients with MDD (n = 16), antidepressant-treated patients with MDD (n= 17), and normal control subjects (n = 50). Patients were evaluated using the Hamilton Rating Scale for Depression (HAM-D). Serum BDNF was assayed with the sandwich ELISA method. Results We found that serum BDNF was significantly lower in the antidepressant-naive group (mean, 17.6 ng/mL; SD, 9.6) than in the treated (mean, 30.6 ng/mL; SD, 12.3; p = .001) or in the control group (mean, 27.7 ng/mL; SD, 11.4; p = .002). There was a significant negative correlation (r = −.350, z = −2.003, p = .045) between serum BDNF and HAM-D scores in all patients. In a preliminary examination, reduced BDNF values of three drug-naive patients recovered to basal levels after antidepressant treatment. Conclusions Our study suggests that low BDNF levels may play a pivotal role in the pathophysiology of MDD and that antidepressants may increase BDNF in depressed patients.