Sufficient blood concentrations of folate and the products from its metabolism arenecessary for several cellular functions. The C677T MTHFR polymorphism, present in over halfof the U.S. population, reduces the efficiency of folate metabolism and has been linked to theonset of multiple psychiatric disorders and cognitive decline. The intracellular parasiteToxoplasma gondii can infect the human brain and is associated with increased prevalence ofpsychiatric disorders and cognitive decline. In vitro studies have found that Toxoplasma gondiimay salvage unmetabolized folate from host cells. Since the C677T MTHFR polymorphism andinfection by Toxoplasma gondii both affect folate metabolism or availability, I used data fromthe third National Health and Nutrition Examination Survey to test the hypothesis that latenttoxoplasmosis and the C677T MTHFR polymorphism interact to predict worse cognitivefunctioning in U.S. adults. I found a statistically significant interaction effect betweenToxoplasma gondii infection and the C677T MTHFR polymorphism in predicting performanceon a test of reaction time. Subjects who were not infected with Toxoplasma gondii experienceddeclines in reaction time with the presence of one or two alleles for the C677T MTHFRpolymorphism. However, this association was reversed for subjects who were seropositive forToxoplasma gondii. No interaction effects were observed when predicting performance on a testof processing speed or a test of short term memory. In conclusion, these findings suggest thatthe co-occurrence of Toxoplasma gondii infection and the C677T MTHFR polymorphism maybe associated with improved reaction time.



College and Department

Family, Home, and Social Sciences; Psychology

Date Submitted


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Toxoplasma gondii, MTHFR, folate, cognitive function, reaction time