Attention deficit hyperactivity disorder (ADHD) is a long-term problem that results in poor concentration and control of impulses. It can affect a child's learning and social interactions, and can have a big impact on family functioning. It's estimated one in 20 children in Australia have ADHD. It is more common in boys than girls. The exact causes of ADHD are unknown, but it tends to run in families, so genes play some part.