Based on our experience I think that some ADHD is actually more of a reaction to poor educational fit than actual ADHD in some cases. I'm not saying that ADHD doesn't exist, I just don't think that there are a lot of other things that look like ADHD but aren't and they get misdiagnosed as ADHD.
I haven't read the study so take it for what it's worth. DS's school was CONVINCED he was ADHD back in grade 1. We have two full psych-ed reports that disagree with that. I don't blame them, he sure *looked* like he had ADHD until we managed to get him to a place where his LD is accommodated and the gifted side is actually challenged a bit. He's a whole different student now that that has happened.
As to whether you should or shouldn't start early I'd say go with your gut. The biggest lesson I've learned over the last few years is that these kids change quick. Find the best fit for now and you can always adjust later if you need to. It is a moving target.
