I think instead that what we've learned to call ADD is instead a number of things all jumbled up together under this simplistic label. I could go on. The point is that the ADD label makes it too easy to ignore what might be going on beneath the surface of things. But perhaps we don't really know at all. Although there is a great deal of support from the medical and scientific community for ADD, once one looks into the literature, things become less clear.
ADD is in the eyes of the beholder.
The behavior rating scales that ask parents to rate their kids on a scale from 1 to 5, for instance, in terms of hyperactivity, impulsivity and so forth, are very subjective and parents and teachers often don't agree on what they see in the same child. The continuous performance tests that are often used to diagnose for ADD are a joke. One of them is a box that sits on a table. The child is told that random numbers will appear in a screen on the box. They are instructed to press the button below the screen whenever a 9 is followed by a 1.