As of 2011 11% of 4-17 year olds were reportedly diagnosed with Attention Deficit Hyperactivity Disorder (ADHD). That’s about 1 of every 9 school age children. Here’s the surprising part: it’s likely that the estimate is low. This is because historically, referral for diagnosis and treatment has been directed to the overtly hyperactive child and often missed the less noticeable inattentive or easily distracted child.