BDNF and depressive disorder: Tsang et al. conducted another meta-analysis and confirmed the association between Val66Met in the BDNF gene and the clinical risk of late-life depression (odds ratio = 1.33; 95% CI = 1.05–1.68; p = 0.02; I2 = 20%; N = 4, 577 patients and 425 control) (11).