Low self esteem can cause depression. It is not just a symptom of something else but an actual problem that can be worked on and fixed but which doesn't require, actually can't really use, the medical profession to fix.

If they said further assessments are required; it sounds like they want you to come back for more/different testing and to see what they might be able to help you with? I would give them a call and ask them what you are supposed to do next?

It sounds like you might want a counsellor from them to help learn how to work on the ruminations and self esteem issues but I think you all have a really long waiting list for counsellors.