I'm certainly no expert, but if you read up on ADHD you'll find that it has a lot of comorbid conditions. A lot of times people will develop depression, anxiety, and other things of that nature if they have ADHD. It's believed that the ADHD at the very least contributes to the development of these conditions.

I believe it has more to do with how the ADHD affects interpersonal relationships and how we handle day to day tasks and the stress that comes along with them than simple lack of concentration. The sad part is that there seems to be a movement to treat the anxiety or depression instead of the ADHD at the root of the problem, essentially switching over to treating symptoms rather than the actual underlying condition.

In answer to your question, I believe that if there isn't a problem with concentration/motivation and you don't have anything hindering you from completing the things that you want or need to accomplish that you'd be far less likely to have to deal with anxiety or depression in the first place. So, I guess concentration does factor into healing in a roundabout way.