MTHFR and depressive disorder: A meta-analysis done by Jiang et al. on a total of 13 case-control studies, including 1895 depressed patients and 1913 controls, found that the T variant of MTHFR C677T gene polymorphism was significantly associated with an increased risk of depression in the Chinese population (T vs. C: OR = 1.52, 95% CI = 1.24-1.85) [32].