DRD4 and attention deficit-hyperactivity disorder: In this study, polymorphisms of genes involved in dopamine circuitry (DRD4-rs916457), synaptic plasticity and working memory (SNAP25-rs362990), and hyperactivity and impulsivity symptoms (ADGRL3-rs2122642, ADGRL3-rs10001410) have been associated with the severity of ADHD under different genetic models of inheritance [54].