Serum levels of brain-derived neurotrophic factor are unchanged after transcranial direct current stimulation in treatment-resistant depression.

BACKGROUND: Brain-derived neurotrophic factor (BDNF) plays an important role in differentiation and repair of neurons in the adult brain. BDNF serum levels have been found to be lower in depressed patients than in healthy subjects. In a couple of studies, effective antidepressant treatment including electroconvulsive therapy led to an increase in BDNF serum levels. As transcranial direct current stimulation (tDCS) is currently discussed as novel therapeutic intervention in major depression, we investigated BDNF serum levels during tDCS in therapy-resistant depression. METHODS: Twenty-two patients with a major depressive episode participated in a double-blind placebo-controlled trial and received randomized cross over treatment with 2 weeks active and 2 weeks sham tDCS (1 or 2 mA for 20 min, anode over the left dorsolateral prefrontal cortex, cathode right supraorbital cortex). RESULTS: Clinical assessment only showed a modest and non-significant improvement in HAMD, BDI and CGI in both groups. BDNF serum levels were measured at baseline, after 2 and after 4 weeks. There was neither a significant change of BDNF levels following active tDCS, nor were severity of depressive symptoms and BDNF levels correlated. LIMITATIONS: The small sample size, its heterogeneity, the short observation period and a cross-over design without an interval between both conditions. CONCLUSIONS: tDCS did not change BDNF serum levels unlike other established antidepressant interventions in this treatment resistant sample. However, larger studies are needed.

Transcranial direct current stimulation in a patient with therapy-resistant major depression.

Transcranial direct current stimulation (tDCS) of the prefrontal cortex (PFC) has been reported to exert significant antidepressant effects in patients with major depression. Several recent studies found an improvement of depressive symptoms in drug-free patients. Here we report the case of a 66-year-old female patient suffering from recurrent major depressive episodes who underwent anodal tDCS of the left dorsolateral PFC over 4 weeks as an add-on treatment to a stable antidepressant medication. Only a modest improvement of depressive symptoms was observed after tDCS, i.e. reduction of the baseline scores in the Hamilton Depression Rating Scale from 23 to 19 and in the Beck Depression Inventory from 27 to 20. However, there was an increase from 52 to 90% in the Regensburg Verbal Fluency Test. In addition, EEG was used to assess the acute effects of tDCS. Low resolution brain electromagnetic tomography (LORETA) showed a left unilateral focal effect (25-40% reduced power) in the delta, theta and alpha frequency bands. The same effect appeared in the surface analysis of the EEG. The absolute, as well as the relative power decreased significantly in the delta, theta and alpha bands after a comparison of the spectral analysis. Though tDCS over 4 weeks did not exert clinically meaningful antidepressant effects in this case of therapy-resistant depression, the findings for cognitive measures and EEG suggest that beneficial effects may occur in depressed subjects and future studies need to further explore this approach also in therapy-resistant major depression.