Attention deficit disorder, which is also called ADD, is a disorder in which a person shows a certain pattern of behavior over time. This pattern includes inattention and impulsivity. Attention deficit hyperactivity disorder, or ADHD, adds hyperactivity to the other behaviors.
In people who have ADD, the brain areas that control attention use less glucose than the brains of other people use. This indicates that the areas are less active. The lower activity level seems to cause inattention. No one knows for sure why these brain areas are less active.
No one knows the exact cause of ADD. Most experts believe that the following factors may play a role in causing ADD and ADHD:
ADD is thought to affect 5% to 10% of school-age children. Boys are 10 times more likely than girls to be affected by ADD.