The effect of depression, BDNF gene val66met polymorphism and gender on serum BDNF levels

Abstract Objective To determine the effect of BDNF gene val66met polymorphism on serum BDNF levels in drug-free patients with major depressive disorder (MDD) and healthy subjects, that differ by gender. Methods Sixty-six drug-free patients (19 males + 47 females) with non-psychotic MDD and fifty-six healthy controls (18 males + 38 females) were recruited. Three-way ANOVA was employed to analyze the effect of mental health status, met-carriage and gender on Hamilton Depression Rating Scale (HDRS) scores and serum BDNF levels, by using the MIXED Procedure (SAS). Results Patients had a lower serum BDNF level than healthy subjects (22.47 vs. 27.49; p < 0.0001). Met-carrier patients had a higher HDRS score than Val homozygote's (25.99 vs. 22.99, p < 0.02). Serum BDNF level for met-carrier subjects (patients + controls) was lower than Val homozygote subjects (23.08 vs. 26.87; p < 0.002). However, there were no effects of two-way interactions of met-carriage and mental health status on HDRS scores and serum BDNF levels. There was no gender effect on HDRS scores in the patients. Overall, male subjects (patients + controls) had a higher serum BDNF level than female subjects (26.87 vs. 23.08; p < 0.002). However, there were no effects of two-way interactions of gender with mental health status and met-carriage on serum BDNF levels. Conclusions We replicated the previous findings of lower serum BDNF levels during depression and in females. In addition, we found that met-carriage had an effect in reducing serum BDNF levels, regardless of gender and depression. Further animal and human studies with a larger sample size should investigate whether BDNF val66met polymorphism could alter brain and serum BDNF levels.