They want everything about your illness and treatment. If you have a psychiatrist, get him involved. It is very likely SSA will send you to one of their psychiatrists for an evaluation.

When I went through the process, I was committed long term to a psychiatric hospital. The hospital staff filled out the paperwork and my guardian signed them. I was approved in less than 4 weeks. It just depends on your circumstances. I did eventually get off disability and go back to work. Disability doesn't have to be forever. It is an essential support sometimes though as you are going through treatment. The more proof of the severity of your illness you can produce the better chance you have. An MD's recommendation is important.