Just because we might not know definitively what causes stuttering does not mean he’s incorrect. With that said, there are doctors and speech pathologists who do point to childhood traumas as the root of stuttering behavior for /some/ people. Dr Martin Schwartz explained that just as some kids tense up their shoulders in anxiety, we tense up our larynx and vocal tract and that this can definitely be due to childhood trauma and early learned behaviors due to stress. I vividly remember some of my childhood traumas from around three to five years old, some incidents directly related to speech, and absolutely believe this to be the reason I developed stuttering. I don’t harbor resentment as this poster does, but wholeheartedly believe if I had been raised in a calmer home, I wouldn’t be a stutter today.