I'm not sure about the psychiatric thing, though maybe. I know he has quite a bad stutter that sometimes comes out during his stand up. He's meant to be a real dick as a person but, even though he had a small part in Phoenix Nights, he completely hates Peter Kay (so he's obviously not completely off his rocker.)
Didn't Stewart Lee say something along the lines of wanting to give up comedy after seeing Kitson for the first time?
I've seen him live a few times. He's very hit and miss, but when he's good he's genuinely on another level.
Anyway, here are some of his podcasts if anyone's interested:
http://www.megaupload.com/?d=6ZMNNSS7
Plus, full stand up at the Cardiff Glee club.
http://www.megaupload.com/?d=FJ8KB8QQ