The neurological theory maked most sense to me, both from the aspect of scientific literature and my own experience. Both from the aspect of different brain function and genetics. I personally have family members that stutter, and many other stutterers do to. At least for me, it's likely genetic. I know that some stuttering is trauma-based, that's been documented, especially among patients with PTSD. But the vast majority seems to be developmental and it mostly starts when children are learning to speak. The fact that certain medications that have an affect on tic disorders also have an affect on stuttering also leads me to believe it's neurological. John Harrison is right that emotions can make it worse, but I don't think trauma causes stuttering in most people. I believe that most stutterers are genetically predisposed to it just like some people are predisposed to neurlogical conditions like BP, depression, Tourette's, etc. At least in my case I thought it started when I was like 10, my parents told me that I had difficulties speaking since I was a toddler, although they couldn't really tell what it was exactly. I just didn't remember it. They even got a developmental specialist.