I know when I had interview, it was recommended to answer the questions directly and to explain relating to the reason I initially filed for disability, in my case it was based on being severe bipolar with major depressive episodes. They want to know your symptoms, prescribed medications and side-effects (impacting you, good/bad), but more importantly how your diagnosis/symptoms impact your ability to sustain work, and why you cannot. Keep the focus on these things. I wrote some of these these things out ahead of time to practice and so I wouldn't forget, sounds silly but I have a really poor memory even about my own self. I can't remember though if I took them in or not.

They are fact finding on your illness and will go over your entire life during this interview; it can be very emotional, don't be surprised by this, but don't try to hide it either. Just answer their questions best as you can and you'll get through it fine. Best wishes.