People with ADD display inappropriate degrees of inattention, impulsiveness and hyperactivity. Inattention is evidenced by being easily distracted, having difficulties sustaining attention in tasks and conversations, failing to finish chores, difficulty planning or following instructions and shifting from one uncompleted activity to another. Impulsiveness is demonstrated by interrupting and intruding without waiting her/his turn in games and social situations. A hyperactive person often fidgets or squirms in seat, has difficulties remaining seated, does not play quietly and does not consider consequences of physically dangerous activities and talks excessively.
Attention deficit disorder is widely recognized in children but underdiagnosed in adults. It is believed that adult hyperactivity is caused by underactivity in one part of the brain, possibly due either to genetic dysfunction or fetal exposure to environmental toxins such as lead, alcohol or cigarettes. ADD can be treated with amphetamine-like drugs to stimulate the brain, which damps down the physical overactivity.
Symptoms of the condition in adults include: an irritable, moody, unpredictable and impatient personality; an intrusive and impulsive behaviour style; difficulty with rules and authority, poor communication skills, intolerance to noise, and inability to handle interruptions. In the USA it is believed that up 60% of children retain hyperactivity traits when they grow older, and can affect as many as 1 in 1,000 people. They are perceived as having personality disorders rather than a medical problems that may be alleviated with drugs. They are often very intelligent but give the impression of being unmotivated and feckless ne'er do-wells.
It is thought that about 6 to 9 million adults in the USA have the disorder.
It is not always easy to distinguish between attention deficit disorder and mania or depression.