Attention deficit hyperactivity disorder (ADHD) is a mental disorder of the neuro type. It is characterized by difficulty paying attention, excessive activity, and acting without regards to consequences, which one otherwise not appropriate for a person's age. Some individuals with ADHD also display difficulty regulating emotions or problems with executive of function. For a diagnosis, the symptoms should appear before a person is twelve years old, be present for more than six months, and cause problems in at least two there settings (such as school, home, or recreational activities). In children, problems paying attention may result in poor learning performance. Additionally there is an association with the other mental disorders and substance misuse. Although it causes impairment, particularly in modern society, many people with ADHD can have sustained attention for tasks they can find interesting or rewarding (known as hyper focus).