"The COMT gene functional polymorphism val158met is one of the most intensively studied variants in psychiatric genetics. Due to small effect size and various methodological issues, its role in various psychiatric disorders and behavioral traits has still not been unequivocally established. In this issue of Neuropsychopharmacology, several studies are presented supporting a role for COMT as a factor in cocaine addiction, brain reward activation, response to tolcapone, distractibility in ADHD, and fMRI bold response. The studies make important contributions to the growing literature that aim to establish an effect of this functional variant on behavioral phenotypes and treatment response."
"Ettinger et al evaluated the effect of val158met on fMRI BOLD response during prosaccade and antisaccade task performance and found differential effects of val158 and met158. Although val158 carriers (homozygotes and heterozygotes) showed lower BOLD response in the prefrontal cortex during antisaccades, met158 homozygotes showed lower BOLD response in postsaccades in the posterior cingulate and precuneus. This differential response is compatible with the hypothesis proposed by Bilder et al (2004) who suggested that val158 and met158 have opposite effects on phasic and tonic dopamine transmission in cortex and subcortical regions, influencing cognitive function and behavior."