I’m on vyvanse I notice I stutter less on it but once it’s wears off at night my speech reverts back to what it normally is. I think the reason I stutter a lil less on the stuff is cos it quietens my head and I can focus on getting my words out easier. When my mind isn’t racing the words just come out a bit better I also find myself not talking as fast as I usually do which probs helps cos I am naturally a fast talker stutter and all