My experience has been different from most comments here. Maybe just bad therapist? I have a v severe stutter. I first went to a therapist when I was 11 and it worked wonders. I was almost completely fluent for a year but then it came back and kept getting worse every year. We were not in a good financial situation to continue therapy again. I got a good job at 23 and went to therapy again. Tried 3 different therapists, one for even 6+ months and my stutter still just kept getting worse. I'm now at a point that I just write to communicate with everyone at my job etc. I just speak with my family and that's pretty bad as well.