It's so strange you should bring that up. I am completely into bodybuilding and have been wondering the same sort of thing. From personal experience, it does not seem to have affected my ability to grow at all. Alcohol, on the other hand, is really really detrimental. I started drinking lots when I first got to college and it really screwed up my workouts to the point where I made no progress at all. But marijuana's all good :rasta: