In relation to neurological function, differences in DNA methylation have been reported between offspring of smokers and non-smokers in the promoters of catechol-O-methyltransferase (COMT) and monoamine oxidase A (MAOA), genes thought to be involved in nicotine dependence and other neurobehavioral disorders [31, 32]. The gene discussed is MAOA; the disease is nicotine dependence.