Previous studies found that DAT1 methylation derived from blood correlated with symptoms of hyperactivity and impulsivity in children and adolescents with ADHD [63] and with impulsivity (and basal ganglia DAT availability) in monkeys [64]; alcohol dependency and alcohol craving [65], nicotine [66] and cannabis [67] dependency in humans. The gene discussed is SLC6A3; the disease is attention deficit-hyperactivity disorder.