Inattentive ADD will soon be called Sluggish Cognitive Tempo (SCT). Russell Barkley among other experts have stopped including the Inattentive subtype of ADHD in discussions about ADHD. It seems that the consensus is that Inattentive ADD is more like SCT than it is like ADHD.
Where it matters, that is, response to treatment, the modalities that work for treatment, the life outcomes, we are more like SCT than we are like ADHD. The experts have been saying forever that the Inattentive type is significantly different from the other types of ADHD and that this subtype is if fact another entity. There has been very little research done on SCT but for lack of another home, we are headed there.
In this 2008 video Russell Barkley speaks for over 15 minutes about Sluggish Cognitive Tempo. In this video he basically reports that Inattentive ADHD is not ADHD at all and that people who are primarily inattentive have a condition that is called Sluggish Cognitive Tempo (SCT).
The SCT that Barkley describes is a disorder characterized by a sluggish sensory processing.
This video is a great outline of what we know about SCT. More research is needed and I believe that research will show that all of us are on a continuum of sensory processing that may be delayed in some areas and normal in others. Recently I read an article that implicated sluggish sensory processing in people diagnoses with dyslexia. We do know that not everyone with SCT or Inattentive ADHD is dyslexic but we also know that there is a fair amount of overlap between these conditions.
A new diagnosis in the DSM V (the diagnostic manual that psychiatrist use to diagnose and treat) will mean more money devoted to figuring out what works for folks like us. That can only be a good thing.