AHRR and attention deficit-hyperactivity disorder: Maternal smoking during gestation isassociated with specific methylation of selected regions ofthe AHRR (aryl-hydrocarbon receptor repressor) and CYP1A1(cytochrome P450, family 11, subfamily A, polypeptide 1)genes in their children with ADHD in the postnatal period(Sengupta et al., 2017).