ADHD stands for attention deficit hyperactivity disorder. It is a medical condition. A person with ADHD has differences in brain development and brain activity that affect attention, the ability to sit still, and self-control. ADHD can affect a child at school, at home, and in friendships. If you think your child has ADHD, make an appointment with your child's doctor. He or she will give your child a check-up, including vision and hearing, to be sure something else isn't causing the symptoms. The doctor can refer you to a child psychologist or psychiatrist if needed.