I stuttered as a child before I can remember anything, based on that I can say that at least in my case it has a neurological origin from birth or early development as a baby. I don't think I have serious issues with comparing myself to others, I do seek a lot of validation though but that comes from being rejected by everyone my whole life lol (not because of stuttering though, I happen to be autistic as well). I don't know, according to psychoanalysis autism is caused by a neglecting mother, but my mom is actually pretty chill. For me it's just plain nonsense.