The gene encoding the enzyme, catechol-O-methyl transferase (COMT), is involved in the degradation of dopamine and other catecholamines. A previous study reported an association between a functional variant of COMT and type 1 alcoholism, which is a late on-set subtype of the alcohol dependence phenotype characterized by harmful drinking to reduce anxiety, which was replicated in an independent study (Tiihonen et al., 1999; Voisey et al., 2011). However, the association between COMT and alcohol dependence was not observed in another independent sample that consisted of mostly families of European and African American descent (Foroud et al., 2007). The discrepancy may be due to allelic heterogeneity at the COMT locus which has several different polymorphisms within the gene. COMT is one of the major genes that modulates dopamine tone in the prefrontal cortex and has a significant influence on cortical information processing/executive functioning. The common COMT functional variant, Val158Met, bidirectionally regulates the enzymatic activity of the encoded enzyme which impacts the efficiency of prefrontal-mediated cognition, specifically executive functioning, working memory, fluid intelligence and attentional control. (Dickinson and Elvevag, 2009). The same
