Genetics of childhood disorders: XVII. ADHD, Part 1: The executive functions and ADHD.

Attention-deficit/hyractivity disorder (ADHD) is a developmental disorder with the cardinal features of difficulties with sustained attention, distractibility, hyperactivity, and impulse control. It arises early in childhood, typically between 3 and 7 years of age. The disorder is relatively stable over time and persists through adolescence and into adulthood in more than half the cases. A significant proportion of children will experience school failure and will develop conduct disorders, delinquent activities, and antisocial personalities. As a result, the burden of ADHD to affected individuals, to their families, and to society is considerable. Over the next several months, this column will explore the underlying mechanisms that contribute to the disorder. The first columns will review the concept of executive functioning and the role the frontal cortex has in regulating mental skills that are required to sustain attention and inhibit impulsive behavior. Particular attention will be given to neurotransmitter systems that are thought to play a critical role in frontal cortical activity. The next 2 columns will be devoted to recent progress in the genetics of ADHD. Finally, we will review whether animal models of hyperactivity have been useful in furthering our understanding of the underlying etiology of the disorder.