Etiology and pathophysiology of adult attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) in adults is a common disorder associated with global and significant impairments in occupational, academic, neuropsychological, and social functioning. However, because the disruptive outward manifestations of ADHD (eg, hyperactivity) decrease with age, adult ADHD remains somewhat hidden and underdiagnosed. One source of confusion about adult ADHD is the controversy about the validity of the disorder, which has been exaggerated by the media but has also found its way into the medical literature. In psychiatry, assertions about the validity of a disorder derive not from a single study, but from a converging pattern of evidence from multiple domains. Some researchers assert that ADHD usually remits in adulthood. If such assertions are correct, adult ADHD should be rare and of little concern to the practicing clinician. But others claim many cases of ADHD persist into adulthood. They stress the diagnostic continuity of ADHD throughout the life span and claim that clinically-referred adults have the same syndrome seen in children. This article first briefly reviews the wide range of data addressing the validity of ADHD and then focuses on studies that have yielded insights into its etiology and pathophysiology.