The role of the catechol-O-methyltransferase (COMT) gene in cognitive function has been the subject of some debate. The gene, which affects dopamine, comes in two flavors: Val and Met. One recent study found no difference between healthy carriers of these two gene variants in terms of cognitive performance, but did find differences in terms of neural activity. Another found that, although the gene did not affect Alzheimer’s risk in its own, it acted synergistically with the Alzheimer’s gene variant to do so. Now an eight-year study of nearly 3000 adults in their 70s has revealed that the Met variant of the COMT gene was linked to a greater decline in cognitive function. This effect was more pronounced for African-Americans. This is interesting because it has been the Val genotype that in other research has been shown to have a detrimental effect. It seems likely that this genotype must be considered in its context (age, race, gender, and ApoE status have all been implicated in research).
(2010). COMT genotype and cognitive function: An 8-year longitudinal study in white and black elders.
Neurology. 74(16), 1296 - 1302.