Hey! Stuttering usually isn’t caused by anxiety but anxiety makes stuttering worse. I stutter (born with it: byproduct of successfully treated apraxia) and I realized that when I get anxious, stressed, angry, or mentally overstimulated I realized that when I stutter and I get self conscious about it it makes my cheek, neck, and tongue muscles tight and those feelings piggy back off of each other which acts as a catalyst for the stuttering which causes it to get worse. What I do to combat this is I use magnesium to calm my mind which allows my words to properly form and be executed. I hope this helps.