ADHD was once considered a childhood disorder. It was thought that individuals outgrew the symptoms associated with Attention Deficit Disorder as they grew into adolescence and adulthood. One of the reasons for this theory is that hyperactivity seems to decrease, as children get older. Research, however, has disproved this theory. Hyperactivity, although sometimes not as prevalent in adults, can often be seen as restlessness or being fidgety.

Some long-term studies show that as many as...