I think NADD is a symptom of something much more serious: integrating the computer into your personal FEEDBACK response loop.

For example, everything you do is in some way a feedback loop. You do something and then it affects you in some way and you might respond to that again by altering the way you do it next time. Well, we've reached the point where computers, EXTENSIONS OF OURSELVES, are more and more tightly integrated into this loop, drastically altering our perspective, behavior, mood, and emotions. Our NADDness is potentially the symptom of that reality manifested... Now whether it actually causes prolonged or even short-term damage to our nervous system probably has to do with the constraints that we are constantly subjected to while using the beasts. Our desktops, our UIs, our browsers, our xterms, our editors... All of these are formally closed systems forcing us to some extent modify our behavior.

From this concept you can infer perhaps why people like Bill Joy argue for responsible use of technology, a re-evaluation of the products we use and how we use them is in order.