BDNF plasma level changes after transcranial direct current stimulation in major depressive disorder

Aims: The brain derived neurotrophic factor (BDNF) is known for almost 30 years. Several investigations described an important role of this neurotrophine not only in fetal brain growth but also in differentiation and repair of neurons in the adult brain. BDNF plasma levels are proven to be lower in depressed patients than in healthy subjects which is supposed to cause a lack of neurogenesis. In a couple of studies, treatment with antidepressants, ECT and TMS led to a significant BDNF plasma level increase. Other studies found no correlation. Method: Here we report the findings of a placebo-controlled, randomized tDCS trial in 20 patients with therapy-resistant major depression. All patients underwent an active 1 resp. 2 mA and sham tDCS over two weeks in a double-blind cross over design. BDNF was measured at baseline, after two, four and six weeks. Results: There was no correlation between severity of depressive symptoms and BDNF plasma level. Overall, clinical improvement by tDCS was modest and did not result in BDNF plasma level increase. Contrarily, tDCS led to a BDNF plasma level decrease by trend. 1 mA and 2 mA tDCS was not superior to sham tDCS in clinical results and BDNF changes. Discussion: Our study population consisted in therapy-resistant patients with probably severily decreased neuronal activity. This might have a restraining effect on BDNF-evoked neuroplasticity. In conclusion, results of BDNF trials are widespread and this question should be addr

This study was supported by Eldith Neuroconn, Ilmenau, Germany