Attention-deficit/hyperactivity disorder: Endophenotypes, structure, and etiological pathways

Several lines of research are revising our picture of attention-deficit/hyperactivity disorder (ADHD). I highlight four emerging themes. First, models from temperament and personality research have been fruitful in clarifying the basic pathways to ADHD and their relation to typical development. Second, many kinds of attention are normal in ADHD, but cognitive control and vigilance are not. These last two are among present candidates for clinical markers that may help identify causes of ADHD. Third, any one cognitive marker pertains to only a subset of the ADHD population; the syndrome's heterogeneity increasingly is a focus of research. Fourth, along with energetic pursuit of genes related to ADHD, resurgent interest in environmental causes of ADHD is notable. New insights into environmental effects are illustrated by recent data concerning lead exposure and ADHD.