I certainly know my clinical anxiety has caused far too many interviews to crash and burn spectacularly. It'll be like "wow, you're graduate educated, 16 years experience, you must be hot shit", and then I go up and just flounder. For me it's not so much writing on a whiteboard, it's having someone standing next to me, or sitting in a chair looking up at me, occasionally interrupting me. I'll try to think out loud and all of that stuff, but that seems to invite questions that sound judgmental to me. I'll start thinking "they don't believe in me, they don't like me, they think I'm a fraud". Unfortunately, I've had those fears confirmed some times too. I had an interview end with a guy saying, as he handed me off to the next person, "You really are the lead of the ... department?"