I think the easiest distinction is the high part. I assume you have never crushed up Ritalin and/or Adderall to snort (I have). The guys taking it non-medicinally get a clear high, and tolerance demands higher doses. The best/worst one is desoxyn. That stuff is heavenly, but so addictive. After scoring a bottle of it I decided that I was never going to take any amphetamine ever again.

From what I understand, ADHD folks do not get the high part, so the addiction risk is not there.