ADHD means Attention-deficit or hyperactivity disorder; it is most commonly found in kids affecting their mental condition. You can also find this mental condition in many teenagers as well as adults. There is an estimate that 8.4 percent of kids and 2.5 percent of adults have ADHD. Attention-deficit/hyperactivity disorder first identified in children of school-aged when it leads to issues with schoolwork as well as disruption in the classroom.