CTNNA2 and attention deficit-hyperactivity disorder: Several GWAS and candidate gene studies describe the association of CDH13 (encodes the cadherin-13 protein) and CTNNA2 (encodes the α2-catenin protein) genes with ADHD or with associated phenotypes (e.g., hyperactivity/impulsivity symptoms; verbal working-memory)45–47 pointing to alterations in the Wnt-associated genes in ADHD.