The symptoms of attention deficit hyperactivity disorder (ADHD) — which include daydreaming, making careless mistakes or taking risks, having a hard time resisting temptation, difficulty getting along with others and fidgeting — can cause challenges, both at home and at school, for the 7 million children who have been diagnosed with the disorder. ADHD has a strong genetic component and is highly heritable, and many children with ADHD have a parent who also has the disorder.