I was diagnosed with ADHD a year ago (ADHD-PI type, especially). It wasn't a surprise for me at all as I had been aware of it way earlier. And I have been stuttering since early adolescence. So I needed to be diagnosed so that I could get medicated. I was started on 30 mg of Vyvanse. The first and second day, it felt like a magic pill. I had such a clear mind, and was able to control my thoughts, hence my words. My stuttering was GONE! I even remember that I said this to my girlfriend sitting next to me in the car, and she got so happy too. For the first time, my brain was CALM... imagine the happiness! I almost cried that all my life I was in a trap and finally got released! well, it took me just a couple weeks. My body started to metabolize the drug, and I needed a higher dose, and so on and so forth. Yes, dopamine really affects. It's not actually too much or too little dopamine, but dopamine dysregulation plays a key role here. That's why sometimes you have clear and smooth fluency, sometimes really bad.