Weed definitely affects my stutter negatively because of the increased introspection, judgement of self and anxiety I get from smoking it. I smoked heavily in my 18-22 years and my speech is a lot better in my later 20s now without weed. You will never know how it will affect you unless you give it real go and stop smoking for a good 6 months. Evaluate yourself before and after, and there will be your answer. There’s a quote that says you can’t keep doing the same thing over and over again, and expect different results.