Russell A. Barkley
It is commonplace for children (especially preschoolers) to be active, energetic, and exuberant; to flit from one activity to another as they explore their environment and its novelties; and to act without much forethought, responding on impulse to events that occur around them, often with their emotional reactions readily apparent. But when children persistently display levels of activity that are far in excess of their age group; when they are unable to sustain attention, interest, or persistence as well as their peers do to their activities, longer-term goals, or the tasks assigned to them by others; or when their self-regulation lags far behind expectations for their developmental level, they are no longer simply expressing the joie de vivre that characterizes childhood. They are instead highly likely to be impaired in their social, cognitive, academic, familial, and eventually occupational domains of major life activities.
Highly active, inattentive, and impulsive youngsters will find themselves far less able than their peers to cope successfully with the universal developmental progressions toward self-regulation, cross-temporal organization, and preparation for their future so evident in our social species. And they will often experience the harsh judgments, punishments, moral denigration, and social ostracism reserved for those society views as lazy, unmotivated, selfish, thoughtless, immature, and willfully irresponsible. These heedless risk-taking children with the devil-may-care attitudes, and self-destructive ways have captured public and scientific interest for more than a century. Diagnostic labels for inattentive, impulsive children have changed numerous times over the last century; yet the actual nature of the disorder has changed little, if at all, from descriptions nearly a century ago (Still, 1902). This constellation of behavior problems may constitute one of the most well-studied childhood disorders of our time. Yet these children remain an enigma to most members of the public, who struggle to accept the notion that the disorder may be a biologically rooted developmental disability when nothing seems physically, outwardly wrong with them.
Children possessing the above-described attributes to a degree that is deviant for their developmental level sufficient to create impairments in major life activities are now diagnosed as having attention-deficit/hyperactivity disorder (ADHD; American Psychiatric Association, 1994). Their problematic behavior is thought to arise early in childhood, and to be persistent over development in most cases. This chapter provides an overview of the nature of this disorder; briefly considers its history; and describes its diagnostic criteria, its developmental course and outcomes, and its causes. Current critical issues related to these matters are raised along the way. Given the thousands of scientific papers on this topic, this chapter must of necessity concentrate on the most important topics in this literature. Readers