BDNF and major depressive disorder: Gender-specific analysis of the cases with severe depression (HAM-D>24) revealed a significant correlation between HAM-D and BDNF serum levels at the entry point among women (Fig 1D; p = 0.0016 p<0.01, n = 28), but no correlation was observed in men (Fig 1C; p = 0.5297, n = 15).