I agree with the two others, it's genetics interacting with environmental factors. I've still had some people say to me "oh, you can get it fixed" and I just look at them. I get that yes in some aspects you can maybe "cure" it, but most of it is people being covert stutterers, and there is nothing wrong with that, all the power to you. I am not one for covering it up and am of the mind that my birth as a premature baby (1lb, 3oz) most likely had some impact in its formation, along with my asthma. I am not one of those who want to erase every trace of it. Why would I hide something that is apart of me and has shaped me into the person I am today? I am not interested in fixing it because I am perfectly fine with living with it. To get rid of it would be to get rid of one part of me as a person. Now, my Stutter is mild compared to others and I am just speaking for myself and other people will see it differently. I am a PWS and I am proud of that.