I've used it therapeutically to help me process trauma which I had been suppressing for decades, and stuttering was tied up with all that. While tripping the emotions came up strong and I used techniques I had learned in therapy to deal with them. It's not a panacea though. Also, don't take psychedelics lightly. They can lead to serious problems for some people if you don't know what you're doing. There are trials going on using it to treat depression, but I don't think there are any trials to treat stuttering. If you're going to do it, do plenty of research beforehand, be in the right headspace and safe environment, and have someone sit with you to make sure you're ok during the trip.