http://www.ssa.gov/pubs/EN-05-10068.pdf

I'm not on SSDI but worker comp and they can send me to an IME every year if they want.

I think with SSDI if you don't have a psychiatrist and they determine you need one, they will send you to one.

Don't worry...there's nothing you can change about the system's process and worrying only upsets yourself.