Definition

Attention-deficit/hyperactivity disorder (ADHD) is a condition that shows up most commonly in boys and girls after puberty begins. Puberty is the period in life when a person's sex hormones become active. ADHD is characterized by an inability to concentrate on tasks, hyperactivity (an abnormally high level of physical activity), and unpredictable behavior. ADHD is known as hyperkinetic disorder (HKD) outside of the United States.

Description

ADHD is thought to affect 3 to 9 percent of all children and is more common in boys than in girls. The signs of ADHD may first appear as early as the age of two or three. In most cases, however, the disorder is not diagnosed until adolescence. Some symptoms of ADHD, such as hyperactivity, tend to disappear in early adulthood. But others, such as inattention to details, remain with up to half of all ADHD individuals throughout their...