Catechol-O-Methyltransferase Polymorphisms and Some Implications for Cognitive Therapeutics

Catechol-O-methyltransferase (COMT) is a gene involved in the degradation of dopamine and may both increase susceptibility to develop schizophrenia and affect neuronal functions involved in working memory. A common variant of the COMT gene (val^108/158met) has been widely reported to affect prefrontally mediated working memory function, with the high-activity val allele associated with poorest performance across a number of tests sensitive to updating and target detection. Pharmacological manipulations of COMT val^108/158met also have reliably produced alterations in cognitive function, in line with an inverted U function of prefrontal dopamine signaling. Furthermore, there is accumulating evidence that COMT val^108/158met genotype may influence the cognitive response to antipsychotic treatment in schizophrenia patients, with met allele load predicting the greatest improvement with medication. Recently, other single-nucleotide polymorphisms (SNPs) across the COMT gene have emerged as possible risk alleles for schizophrenia, although little is known about whether they affect prefrontal cognition in a manner similar to COMT val^108/158met. Preliminary evidence suggests a modest role for a SNP in the 5′ region of the gene on select tests of attention and target detection. Haplotype effects also may account for a modest percentage of the variance in test performance, and are an important area for future study.