Thanks benjojo!
I think you're right, depression can have different causes throughout life. My feeling is that what is diagnosed as clinical depression, and includes suicide ideation or self-harm, has compound causes that lead back to early trauma(s). In other words, the childhood mistreatment led to belief systems that led to compound trauma. Everything from subsequent failed relationships (re-enactments) to a job a person hates (unconscious re-creation of the family home). Although these additional factors feed the depressive state, the root of it lies somewhere long ago. And, I feel, the way out is to trace the power cable back to where it was first plugged in.
Thanks for reading and your wise thoughts.