I do know there are certainly physical impairments that cause stuttering, one of my good friends growing up, his father fell through the ice in Lake Michigan where I grew up, and he developed a stutter because of that. A lot of these people who have been “born” (as I grew up explaining to people) with stuttering can learn to control and cope with it, while those who have been born with or have experienced an incident that resulted in stuttering may not be able to deal with it as easily as others. My father is a physician and was present during my birth and has told me a lack of oxygen at birth caused me to develop a stutter, whenever I talk to myself, sing to myself or even sing around others, I never stutter or stammer. Lots of people can overcome this if they just have the willpower to, I did not deny there are physical impairments of damage people causing them to not be an able to overcome their stuttering. Confidence in yourself and your ability to speak to others goes an enormous way to helping people overcome something very personal to them. Edit: wording.