more than the official classification would let you believe:
http://www.pnas.org/...09/17/6769.full
what it's impressive about this study, they used no novel or hi-tech methods, save for new way of organizing data.
they went on to say:
extending the present approach to neuroimaging studies may accelerate such characterization and inform heterogeneity in the neurobiology underlying the typical developing and ADHD populations (42, 43). This approach would allow for a more streamlined procedure to help investigators target and test theories related to multiple unique pathways or circuits related to ADHD (42, 43). Indeed, the same methods may be well suited to categorize participants on the basis of the neural circuitry itself or genetic markers (or pathways) rather than neuropsychological domains. We hypothesize that each group identified here is represented by distinct, multiple brain profiles.
i have a feeling the work of Dr Daniel Amen will be vindicated in the future. every new discovery is initially faced with resistance of the establishment.