ADHD isn't about age, it is about amygdala sensitivity and compensating behavioral habits, like shying away, avoiding eye contacts and playing alone with/in own imagination.
I am in the middle of being diagnosed with ADHD (I'm 30). It was actually HN that prompted me to take action, but that's another story which I can expand on if anyone is interested.
I haven't read much about ADHD being linked to shyness and introversion, although I certainly haven't done enough research. But it describes me very well, could you possibly say a little more or point me to some resources? Everything I've read talks about impulsiveness and extroversion. I would guess that shyness and introversion are learned reactions to the impulsiveness.
http://www.amazon.com/Emotional-Intelligence-Matter-More-Tha... is a good starting point.
I think everyone involved (I'm with Asperger's) should study the topic, to be able to understand (and then make a corrections to) one's own behavior, instead of believing what other people (including doctors) are saying.
I didn't word my question very well. I was wondering where you got your examples. None of the ADHD info I've read says anything about shyness or eye contact. A child playing by themselves would seem to be the exact opposite of the popular notion of what a kid with ADHD is like (assuming that they weren't totally spaced out to the world around them, which you didn't mention).
I'm just interested because that's me. I'm shy, I have minor problems with eye contact (more like I just have problems relating to new people) and I spent a large chunk of my childhood playing by myself with Legos and Transformers. That last bit was one of the reasons my parents said they didn't think I could have ADHD. "But you used to amuse yourself for hours by yourself. You certainly were paying attention to THAT."
Mood, anxiety, and personality disorders also frequently occur along with ADHD[2].
[1]: http://www.webmd.com/add-adhd/guide/types-of-adhd
[2]: http://www.mayoclinic.com/health/adult-adhd/DS01161/DSECTION...