What causes ADHD?

Attention deficit hyperactivity disorder (ADHD) symptoms—inattention, impulsivity, and/or hyperactivity—affect a child's ability to learn and get along with others, some people think an ADHD child's behavior is caused by a lack of discipline, a chaotic family life, or even too much TV. In fact, research suggests that ADHD is largely a genetic disorder. http://www.health.com/health/gallery/0,,20441463,00.html However, some environmental factors may play a role as well.