1992). Although it is most well‐known for synthesis of DA and serotonin in the central nervous system, the enzyme is also located in pancreatic β cells where it is theorized to be involved in local, dopaminergic regulation of insulin secretion (Rubi et al. 2005; Ustione et al. 2013). The abundance of nominal associations in the DDC gene in a T2D population has biological relevance with regard to potential roles in cognitive function as DDC deficiency due to frame‐shift mutations or substitutions leads to impaired cognitive function (Bertoldi 2014). This evidence concerns the gene INS and type 2 diabetes mellitus.