I don't think anyone has mentioned ADHD-PI (Predominantly Inattentive). It's like normal ADHD but trades the hyperactivity for inactivity, which means its more difficult to identify.
I tried some adderall on advice of my sister and the result has been life changing. Anyone that heard I was on ADD meds would say "well geez I wish I could concentrate better, too." I gave some adderall to one of my friends to see if it would help him concentrate and guess what? All it did was get him high. YES ADHD misdiagnosis may be rampant but ADHD-PI diagnosis is largely absent.
When a Banker jumps out of a window, jump after him--that's where the money is. -- Robespierre