I think stuttering can be caused by things like childhood trauma, but I've thought about it a lot and I think it's purely neurological. Let me explain - breathing is something humans do without even thinking about it, just like how our hearts pump blood, etc. There's a word for it but I can't think of it. I think that most stuttering is mainly a problem with us not breathing correctly. A lot of times when I stutter, I notice I'm out of breath or when I come close to the end of a sentence I notice I start to have some sort of trouble breathing. I think our brains aren't exactly wired correctly in terms of breathing and speaking at the same time. It's something in the brain. When you sing, you have to breath a certain way and I'm one of those stutterers who doesn't stutter AT ALL when I sing. This was a major factor in my theory.