['Apolipoprotein E epsilon-4 (APOE ε4) allele, methylenetetrahydrofolate reductase (MTHFR C677T), and methionine synthase (MTR A2756G) were tested their associations with cognitive impairment in people with late-life depression (LLD).', 'People with LLD were assessed by mini-mental state examination and were examined the distribution of APOE ε4 allele, MTHFR, and MTR polymorphisms.', 'Odds ratio of MTR 2756 AA to MTR 2756 AG and GG genotypes for the risk of cognitive impairment was 5.80 (95% confidence interval\u2009=\u20091.18-28.50; P\u2009=\u20090.03).'] Is methionine synthase 2756AA polymorphism associated with the risk of cognitive impairment in patients with late-life depression?