While retrospective observational studies have suggested that self-reported perinatal folic acid supplementation can improve maternal depression symptomology several months postpartum, especially in women with a MTHFR TT genotype [28] our findings suggest that women with a TT genotype do not demonstrate an inverse relationship between physiological folate and mood symptoms (i.e. mania and perhaps, depression). This evidence concerns the gene MTHFR and depressive disorder.