I think that there's something very unnatural about a lot of these intellectual tasks that are set before us every day. We definitely did not evolve to write emails for six hours a day, but that's more or less a necessity of modern life for most people. And stimulants really help with sustained periods of writing and reading. I think a lot of what is typically diagnosed as ADHD may just be a sort of a version to this very unnatural need to sit in front of a computer writing and reading non-stop for multi-hour stretches.