ADHD medication includes Ritalin and Adderall. Both have stimulant/amphetamine like effects to those without ADHD.
You can see the window for abuse and addiction here is pretty huge.
Children misdiagnosed with ADHD can get hooked on this stuff (I don't have a source for that, but its what I've heard).
More commonly, college/highschool students can get them pretty easily to cram for an exam or finish an assignment in one night, or at least that's what they're told by movies and TV (but I'm told by a friend that it really is effective in getting a lot of work done in a small timeframe).
Not sure about ADHD but there have been several anecdotal evidence of magic mushrooms helping reduce or in some cases eliminate Autism symptoms. Bear in mind that Autism is a spectrum and not everyone will react the same way
Could you expand on the ADHD bit? That sounds interesting as its not something I've heard a lot about.