It doesn't show that at all. It could mean that that profession selects people who are the best in the world at those things, and cannabis is entirely coincidental.

> You see, I think drugs have done some good things for us. I really do. And if you don't believe drugs have done good things for us, do me a favor. Go home tonight. Take all your albums, all your tapes and all your CDs and burn them. 'Cause you know what, the musicians that made all that great music that's enhanced your lives throughout the years were rrreal fucking high on drugs. The Beatles were so fucking high they let Ringo sing a few tunes.

-- Bill Hicks

Well, supposed effective prevention for the supposed effect.