The diagnosis of Attention Deficit Hyperactivity Disorder (ADHD) has changed greatly through the years. A century ago, it didn’t even exist. One of the first references to children who were unable to concentrate, hyperactive and displayed problems with learning was in 1902 . DSM-I made no reference to the diagnosis. The closest diagnosis clinicians could cite was Minimal Brain Dysfunction , which was used to describe children who had hyperactive and impulsive behavior. The syndrome was thought to be of organic etiology.