Attention deficit hyperactivity disorder, or ADHD, is a disorder in which an individual consistently shows certain behaviors over time. The three categories for these behaviors are inattention, hyperactivity, and impulsivity.
In people who have ADHD, the areas of the brain that control attention use less glucose than the brains of other people. 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 ADHD. Most experts believe that the following factors may play a role in causing ADHD: