CACNA1C was also recently identified in the largest human genome-wide association study to date as one of only two genes presenting a common risk factor across five major forms of neuropsychiatric illness: major depression, schizophrenia, bipolar disorder, autism, and attention deficit hyperactivity disorder (ADHD; Cross-Disorder Group of the Psychiatric Genomics Consortium, 2013). This evidence concerns the gene CACNA1C and attention deficit-hyperactivity disorder.