For example, studies showed that the MAOA is associated with ADHD by Pedigree-based generalized multifactor dimensionality reduction (PGMDR) on 1462 ADHD children and 807 unaffected controls, [3] while another study found that MAOA variants may be associated with sustained attention deficit by genotyping DNA from ADHD children (n = 242) which evaluated the attention deficit by a digit cancellation test [21]. Here, MAOA is linked to attention deficit-hyperactivity disorder.