TL;DR at the end. I went to a hypnotherapist when I was 15 or 16. I'm not a strong candidate for hypnosis because I've always needed to keep my wits about me, but I followed the guidance anyway. My memory is a bit hazy because it was 30 years ago but it went something like this. He asked me to think back to when it started, something like a triggering event. I remembered a traumatic experience when I was little, involving my mum as an (unintentional) instigator. I didn't actually say anything when he asked because my mum was in the room as I wasn't an adult. I even thought to ask, "Am I supposed to say this out loud?" but I stayed quiet, not really wanting to blame my mum. Eventually the therapist gave a big sigh as I wasn't responding. My mum later asked why I didn't say anything and I lied, saying I couldn't think of anything, which she thought was good that nothing bad happened. In hindsight, this was the worst thing I could have done as I wasn't engaged in what might have been part of the solution. I had a bunch more sessions, now focusing more on relaxing and I suppose trying to alleviate anxiety. I was meant to listen to the tapes at home, but to be honest, that first question was the key to everything. As I later learned about psychoanalysis I began to pick apart various childhood traumatic incidents, finding clear links between them my dysfluent speech. I struggled on my own for far too long, too scared to actually deal with these issues, sinking deeper and deeper into depression. I eventually sought counselling, which was middling, and later specialist trauma counselling, which was really helpful. Before and after counselling, I had been working on other aspects of my mental health, finding improvements in speech with each breakthrough, but it was resolving my traumas and inner conflicts which yielded the greatest results. TL;DR: I didn't allow hypnosis to work, but one question in the first session was the key to understanding my trauma-induced stammer.