In the mid-1970s, attention-deficit/hyperactivity disorder (ADHD) was still believed to be a childhood disorder that disappeared with the onset of adolescence. At this time, Wender studied a cohort of adults presenting with ADHD-like symptoms, all of whom had been diagnosed with ADHD in childhood. Wender prescribed psycho-stimulants, which successfully produced a response in the adults, thus fostering research into adult ADHD.

Until recently, little was known about the epidemiology of attention-deficit/hyperactivity disorder (ADHD) in adults. Bottom-up studies following children with ADHD into adolescence had shown variable rates of persistence, some of which depended on the definitions used. The traditional diagnosis was complicated by the introduction of the Diagnostic and Statistical Manual of Mental Disorders, Third Edition, which stated that ADHD could be diagnosed with inattentive symptoms alone. This resulted in diagnostic inconsistency as earlier investigations demanded the presence of hyperactivity while others did not. Diagnosis also depended on the site, the cohort, whether interviews versus rating scales were employed, and whether the subject or their parent were the source of information.

Attention-deficit/hyperactivity disorder (ADHD) is present in 4% to 6% of adults in the United States. In the National Co-morbidity Survey Replication, a diagnosis of ADHD was associated with greater marital problems, unemployment, difficulties in the workplace, and frequent workplace absence. Despite these findings, the body of knowledge regarding impairment in adult ADHD is far from complete. Building upon our knowledge of impairment in adults with ADHD will result in a broader range of treatment outcomes which may be measured and targeted.

Attention-deficit/hyperactivity disorder (ADHD) is highly co-morbid across the life span. However, co-morbidity is not uniform across time; individual co-morbid conditions tend to occur at different times developmentally, with rates often reflecting lifetime occurrence (Slide 1). In addition to changes in the rates of co-morbidity, the nature of co-morbidity may also differ in late adolescence/adulthood, when co-morbid conditions can be especially impairing (eg, antisocial disorder, substance use disorder [SUD], more severe mood disorders).