ADHD is quite common; it is conservatively estimated to affect 3% to 5% of school-age children. Some reports suggest that as many as 4% to 8% or even an amazing 10% to 18% of children have ADHD. Thus, somewhere between 2 and 13 million American children have ADHD. Put another way, on the average, at least one child in every classroom has ADHD. ADHD results in millions of physician visits per year.
Approximately 60% of children with ADHD have symptoms that persist into adulthood. This means that close to 8 million adults (about 4% of the U.S. adult population) have ADHD. However, as ADHD is a behavioral disorder still lacking a specific biological marker, estimates of its frequency can be affected by a number of factors.
The method for making the diagnosis most certainly affects the estimated frequency. The current DSM-IV-TR standards, which allow both hyperactive–impulsive and inattentive subtypes, have resulted in higher rates of diagnosis than previous DSM standards, which placed a higher emphasis on hyperactivity as a diagnostic criterion. In other words, the frequency of the diagnosis increases when hyperactivity is not regarded as a necessary characteristic for ADHD diagnosis. The looser the requirements are, the greater the number of individuals included under the diagnostic umbrella.
The estimated frequency of ADHD also depends on who provides the information to make the diagnosis: parent, teacher, child, or physician. All have their own agendas to report. Teachers are seeing children through the lens of the classroom, where there are specific academic and behavioral expectations. In a class full of children, disruption by a single student can have a ripple effect. On the other hand, in a large class full of children, teachers may not notice the quietly inattentive child. Children may be less aware of their own symptoms. Adolescents, in particular, are notorious for underreporting and minimizing their symptoms. Parents view their children’s behavior from the perspective of day-in, day-out living. Their perspective is intensive as well as long-term. On the one hand, they may minimize symptoms that they have been living with for years. On the other hand, the behavior seen under the intensive lens of daily living may make them keenly aware of things that go unnoticed by others. Physicians see children in a rather artificial setting, where the child is the focus of attention and may be on his or her best behavior. Conversely, some children are stressed by a visit to the doctor and will immediately demonstrate ADHD-like signs by wandering around the office, touching and picking up everything in sight.
