The Attention Deficit Hyperactivity Disorder (ADHD) diagnosis persists despite it possibly being the most unsophisticated notion in mental health for the past two-hundred years. In the late 1700s an English physician described the symptoms as "mental restlessness." In early 20th century America it was described as Minimal Brain Dysfunction (MBD) of which a Harvard psychiatrist remarked that any doctor who uses this diagnosis has a minimal brain dysfunction (a cute remark, I think). ADHD is merely its latest incarnation and makes no sense with more diagnoses on the East Coast than the West Coast and more boys than girls, apart from its symptoms being identical to anxiety and depression.
In both children and adults, when these symptoms are present and not related to real worry or unconscious conflict, they reflect Elements of a Borderline Psychotic Psychostructural Organization. Which does not mean Psychotic or Borderline Psychotic but rather a weakness of basic ego capacities because of faulty early developmental experience which occur during the first three years of life and affect the development of reality testing, mood regulation, sense of self, and control of behavior and thinking.
The ADHD diagnosis has persisted, I believe, for a number of reasons:
1. Large, profitable mental health and pharmaceutical industries have grown up around it.
2. Ego psychology has grown out of favor with a consequent dearth of education of clinicians on sophisticated early life ego and child development. My (long deceased but still mourned) doctoral advisor once said that to understand human behavior one must go to psychoanalytic concepts, that there is simply no where else to go, and I agree.
3. Sixty years ago most psychiatrists provided therapy but today few do, apart from those who have had psychoanalytic training and these are not many. Thus, apart from reasons 1 and 2, they prescribe drugs. Which, alas, some parents demand and doctors comply. As a mother once said to me, she would rather that her child had a brain tumor than an emotional problem since a tumor could be cut out. Most new patients don't know what therapy is and must be educated.