The COMT gene provides instructions for making an enzyme called catechol-O-methyltransferase. In the brain, catechol-O-methyltransferase helps break down certain neurotransmitters - chemical messengers that conduct signals from one nerve cell to another. Catechol-O-methyltransferase is particularly important in an area at the front of the brain called the prefrontal cortex, which organizes and coordinates information from other parts of the brain. This region is involved with personality, planning, inhibition of behaviors, abstract thinking, emotion, and working (short-term) memory. To function efficiently, the prefrontal cortex requires signaling by neurotransmitters such as dopamine and norepinephrine. Catechol-O-methyltransferase helps maintain appropriate levels of these neurotransmitters in this part of the brain.

The COMT gene is composed of two alleles, Val and Met. The Val allele is associated with higher dopamine levels, while the Met allele is associated with lower levels. Studies have found that individuals with the Val/Val genotype tend to be more risk-taking, impulsive, and novelty-seeking than those with the Met/Met genotype.

In addition to influencing personality traits, the COMT gene has also been linked to cognitive performance. Studies have found that individuals with the Val/Val genotype perform better on cognitive tasks than those with the Met/Met genotype. This suggests that the Val allele may be beneficial for cognitive performance.