The specific percentage of depression that comes from abuse is not given. However, studies have shown that different people find different ways to cope with the situation they face. Adult women easily fall into depression from abuse as compared to men.
Good question but because everyone deals with the pain differently it's hard to put a percentage to it plus it's hard to tell if your depression is a medical issue or if it is from past abuse. The only way to find out is to see someone about it. Go to a therapist, start dealing with your issues and get on some meds if you need it.