Makes sense, actually; dopamine is highly implicated in both disorders. ADHD responds to stimulants because they increase dopamine. Unfortunately they can also cause psychosis in large enough doses (common problem with meth and cocaine use). Antipsychotics, which reverse the psychosis... cause pseudoparkinsonianism, or drug-induced Parkinsons. Not sure exactly how this part of the puzzle fits in, but I've definitely seen some other puzzle pieces from that corner, to extend the metaphor.