[pdpi]

You have a set of diagnosis criteria, and matching those criteria gets you the ADHD diagnosis. This study takes people who fit the diagnosis, and says there's a test you can do to split those people into three groups.

But yes, once they have a better understanding of what that difference means, the next step might well be to split the ADHD diagnosis into two separate disorders, or even that, like cancer, ADHD is actually a whole range of separate but related conditions.