Since patients with 22q11DS have only one copy of the COMT gene, which is associated with reduced COMT gene expression (van Beveren et al., 2012) and enzyme concentrations (Gothelf et al., 2014), they may consequently be chronically exposed to abnormally high DA levels (Boot et al., 2008), particularly in the PFC. This evidence concerns the gene COMT and 22q11.2 deletion syndrome.