In my experience psychiatrists don't know the first thing about my speech disorder. I have been able to independently prove time and time again that mine at least (I block, for the record), is completely psychological as far as control of the blocking mechanism goes. Under certain conditions I am consistently 100% fluent, and others consistently disfluent, and there is always an obvious and direct correlation to my current level of anxiety. Speech therapy didn't help me at all as a kid either, but I'm sure part of that is because I didn't understand my impediment at all and was extremely embarrassed by it. The other part is that my speech therapy didn't address the anxiety factor at all and focused on teaching me how to form shapes with my mouth and breathe.