Its all tied to stimulation. Less stimulation during summer break compared to peak stimulation during exam periods/deadlines. Its normal for all stutterers and kind of unavoidable. My stuttering goes down significantly when I am off school during the summer. I wouldn't say treating anxiety/stress would make the stutter go away, I have significantly less anxiety now than during my early twenties but still struggle with stuttering. The only difference is I care less about it and don't get as stressed when I stutter.