People with attention deficit hyperactivity disorder (ADHD) have trouble paying attention and sitting still, and they can be impulsive, acting without thinking about the results, sometimes with dangerous results.

ADHD is often diagnosed in children but also affects adults. Some children with ADHD can have difficulty in school or trouble making friends.

ADHD is not contagious; people are born with it. It often runs in families.

Different people display ADHD in different ways. Most have problems concentrating and paying attention, sitting still in class or at work, and waiting their turn. They can be disorganized, distracted, or forgetful, and tend to daydream in class or at work. They might lose things and have trouble finishing assignments, move around a lot, talk too much, or interrupt other people’s conversations.