ADHD is a mental illness that is quite prevalent. About 250,000 Danes have ADHD. The illness begins in very early childhood, before school age. The classic symptoms are an easily-awakened distractibility, concentration difficulties, hyperactivity, inner restlessness and impulsiveness.
People with ADHD are typically not very focused on the future. They are highly impulsive and live in the present. The diagnosis for this and most other mental illnesses is based on the clinical picture. It is important that the symptoms are present in all possible situations and throughout life, in contrast to bipolar affective disorder, in which concentration difficulties and impulsiveness are related to instability of mood.
Many with ADHD develop serious learning difficulties and have problems getting through school. Criminal behavior is often seen, and many end in substance abuse.