attention-deficit hyperactivity disorder

Psychiatric condition occurring in young children characterized by impaired attention and hyperactivity. The disorder, associated with disruptive behaviour, learning difficulties, and underachievement, is more common in boys. It is treated with methylphenidate (Ritalin). There was a 50% increase in the use of the drug in the USA in the period 1994-96, with an estimated 5% of school-aged boys diagnosed as suffering from ADHD. In 1998, the number of children and adults in the USA taking medication for ADHD (mostly Ritalin) was approximately 4 million. In the UK, the prescription of Ritalin doubles each year.

Hyperactivity was first clinically diagnosed in 1902 and information has been gathered on the subject since then. The condition was formally called ADHD in 1994. In 1996, US researchers found that 50% of children diagnosed as ADHD sufferers carry a gene that affects brain cell response to the neurotransmitter dopamine. The same gene has also been linked to impulsiveness in adults. Diagnosis requires the presence, for at least six months, of eight behavioural problems, first developing before the age of seven. In addition to their hyperactivity, such children are found to be reckless, impulsive, and accident prone; they are often aggressive and tend to be unpopular with other children. The outlook for ADHD sufferers varies, with up to a quarter being diagnosed with an antisocial personality disorder as adults.