I'm a stage performer, and my stutter actually goes away when I'm in front of an audience performing. Albeit my shows have lots of music and distractions but it works. Stutters are typically psychophysiological, so they are completely involuntary. Stress and pressure do make blocks worse, but it doesn't appear to be the actual cause of the disorder. And because there are various forms of stuttering, they don't all have the same cause. But you could be right in regard to the stutters that were caused by trauma. Anxiety induced situations cause it to act up heavily.