Saying that anxiety causes/triggers stuttering is like saying that the lightning causes/triggers the thundering.
They think that anxiety is the charge of the elements in the sky – but they're wrong. It's the lightning, even if it sometimes light the whole sky.
That's why Pagoclone and other medicines can't cure stuttering.
Lightning is the fear/anxiety of stuttering. When we're going into a hard speaking-situation, the world shakes for a moment. After that comes the cramp in our stomach, the tension in our muscles etc., we all know these things which are variable of course. At times we manage to speak well, and the sky lightens up. But if we don't, then: BANG!
It's the same as in love. When we see the loved one, comes the lightning. Then comes the stress. Then we win or fail.
Everybody talks about stuttering – and nobody considers seriously that we have been speaking fluently a lot. I'm now almost completely mute, my stutter is that severe, but I've lived 15 years with a covert stutter which is challenging of course and stressful, but imagine how many success you gain either! I'm mute because I was very fluent, "I had the best girl in my town"!
So: you're on wrong track if you examine the lightning to explain stuttering. "I didn't get the girl, because I was anxious" – aha of course buddy, but the truth is that you were anxious because you wanted the girl badly. Don't blame anxiety. It's not the cause. And not the trigger either; when anxiety comes, the trigger had already been pulled. I wonder, again, why.