ADHD is divided into 3 subtypes: symptoms of hyperactivity, symptoms of inattentiveness, or symptoms of both.

Researchers have found that genes make it more likely to develop ADHD. Studies have shown that the disorder has a genetic link. Sometimes parents are found to have the disorder when their child is diagnosed with the condition.

Symptoms can appear as early as between ages 3 and 6, the National Institute of Mental Health says. They can also appear later in childhood and into the teen years.

Stimulant medicines reduce hyperactivity and impulsiveness. They also make it easier for the child to focus, learn, and stay calm. Some children can't use stimulants. For them, other medicines are available. Which medicine is prescribed depends on the child. What works for one child may not work for another.

Behavior therapy teaches kids how to control their behavior. Parents can learn how to use a system of rewards and consequences to change a child's behavior. Through this system, a parent gives positive feedback right away for behavior that needs to be encouraged. It ignores or redirects behavior that should be discouraged. Parents can also learn how to restructure a child's time or tasks so the child does not feel overwhelmed.