If your panic attacks and anxiety prevent you from living a "normal" life (but normal is all relevant, of course), and your dog helps to prevent that feeling of anxiety and panic attack, then absolutely it would qualify as a disability. There are service dogs working right now with people with panic and anxiety attacks.
http://www.iaadp.org/psd_tasks.html - particularly III. COPING WITH EMOTIONAL OVERLOAD
http://www.standardpoodlesusa.com/se...d-bipolar.html
http://news.medill.northwestern.edu/....aspx?id=79757
http://www.psychdog.org/
http://www.psychdog.org/training.html
There are many more links you can find if you Google "Service Dog for Panic Attacks".
I volunteer with Canine Assistants in Alpharetta that trains service dogs for the physically disabled. We don't do psychiatric service dogs though.