Attention-deficit hyperactivity disorder (ADHD) represents one of the most common and serious neurobehavioral disorders of childhood, affecting children from early childhood into adult life. The cardinal clinical characteristics of the disorder, inattention and, at times, impulsivity and hyperactivity, may interfere with the child's adjustment in every phase of existence, both through time and across experiences. Though its etiology may involve environmental influences,1 evidence from a number of lines of investigation suggests that biologic factors play an important role in a significant number of cases (S.E.S. and B.A.S., in press).
The entity we today label ADHD has undergone multiple transformations over the past century. Some of these are semantic; others, however, are more substantive and reveal significant changes in our understanding of the disorder. Review of the evolution of these changes provides important insights into the current conceptualizations of the disorder.
The origins of ADHD can be traced to the