Different serum BDNF levels in depression: results from BDNF studies in FYR Macedonia and Bulgaria.

BACKGROUND A growing body of evidence shows that brain-derived neurotrophic factor (BDNF) plays a role in depressive disorder. Serum BDNF levels are lower in depressed patients and they increase after a long course of antidepressant treatment. Our study aims to test the effect of antidepressant treatment on serum BDNF levels in patients with a depressive episode, after they have achieved remission in two studies in Macedonia and Bulgaria. SUBJECTS AND METHODS In the Macedonian study 23 patients were included (11 female, 12 male) diagnosed with a first depressive episode according to ICD-10, as well as 23 control subjects age- and sex-matched without a history of psychiatric disorder. In the Bulgarian study 10 female patients with depression and 10 control subjects were included. We have applied the Hamilton Depression Rating Scale (HDRS) to assess depression severity. Blood samples were collected before antidepressive treatment and after remission was achieved (decrease to 7 points or less on HDRS). RESULTS In the Macedonian study, mean serum BDNF level at baseline was 13.15±6.75 ng/ml and the mean HDRS score was 28.52±4.02. Untreated depressed patients showed significantly lower serum BDNF levels compared to the control group (25.95±9.17 ng/ml). After remission was achieved, the mean serum BDNF level was 24.73±11.80 ng/ml whereas the mean HDRS score was 7.04±3.15. After 8 weeks of treatment there was no statistically significant difference in the serum BDNF levels between the two groups. In the Bulgarian study, baseline mean serum BDNF levels were 26.84±8.66 ng/ml, after 3 weeks treatment and remission was achieved mean serum BDNF levels were 30.33±9.25 ng/ml and in the control group mean serum BDNF levels were 25.04±2.88 ng/ml. Integrated results showed baseline mean serum BDNF levels of 17.30±9.66 ng/ml, after achieved remission 26.43±11.25 ng/ml and in the control group mean serum BDNF levels of 25.68±7.76 ng/ml. CONCLUSION The Bulgarian results showed no statistical difference between the depressed group and controls. The Integrated results and the Macedonian study supported previous findings of low BDNF levels in untreated depressive patients compared to healthy controls, and that those levels increase after antidepressant treatment. These results may suggest that low serum levels of BDNF are a state abnormality that is evident during depression and normalizes during remission.