ISSUES IN THE DEFINITION AND CLASSIFICATION OF ATTENTION-DEFICIT DISORDER

This article examines the inextricably intertwined issues of definition and classification of attention deficit disorder (ADD), emphasizing the heterogeneity embedded within the diagnosis of ADD. Using data from our ongoing investigations we have focused on the overlap of ADD with reading disability as a heuristic example illustrating the consequences that heterogeneity has on a range of findings, including prevalence and the association between inattention and measures of language and reading. We propose and describe a systematic classification study whose goal is the development of a unitary, empirically derived classification for ADD, a classification that should increase the consistency and generalizability of findings across investigations and across disciplines.