Combined ADHD Subtype Confusion

I have recently read two papers where the researchers believed that most people classified as primarily Hyperactive/Impulsive were actually, on closer examination, the Combined type of ADHD. These researchers felt that when you looked at the symptoms of the Hyperactive/Impulsive subtype carefully, these patients had enough inattentive symptoms to actually put them in the Combined category. Other researchers feel that with age, all Hyperactive/Impulse patients morph into the Combined profile.

Researcher believe that a defect in the dopamine transporter gene causes hyperactivity and a defect in the norepinephrine transport gene causes innattentiveness. New research has found that the Combined type has a problem with the choline transport gene.

If there are really genetic variations in each subtype than the ideas that most of the Hyperactive/Impulsive subtype will, with age, Morph into the Combined type cannot be correct and the genetics of these two subtypes needs to be questioned.

I think that it would be tidy to find a gene to blame on each of the subtypes but my guess is that it will not be that cut and dry. I see many people classified as primarily hyperactive with enough inattentive symptoms that I consider them to be more correctly classified as in the Combined subtype and I think that the Hyperactive subtype and the Combined subtype are hard to classify as one or the other.



This is not the case for the Primarily Inattentive subtype. There is far less ambiguity regarding this subtypes symptoms so maybe the genetic work being discovered for this subtype will be easier to interpret.