Functional gene variants in MTR (rs1805087), CBS (rs5742905), MTHFR (rs1801133 &rs1801131), MTHFD (rs2236225), RFC1 (rs1051266), plasma vitamin B12, folate and homocysteine were analyzed. rs1805087 'A' showed strong association with ADHD.
We hypothesized that ADHD related cognitive deficit could be attributed to abnormalities in the folate cycle and explored functional single nucleotide polymorphisms in methylenetetrahydrofolate dehydrogenase (rs2236225), reduced folate carrier (rs1051266), and methylenetetrahydrofolate reductase (rs1801131 and rs1801133) in families with ADHD probands (N = 185) and ethnically matched controls (N = 216) recruited following the DSM-IV.