Indeed. I, as many others I'm sure, have always wondered if my inability to concentrate was ADHD (although I'm sure it's not). I liked the other article today (link: http://news.ycombinator.com/item?id=570893) about focus. I'm going to pick up a few of those books to see if I can get inspired, although I believe the key is doing concentration calisthetics.
Regarding other drugs and intellectuals, this article comes to mind as well: