This piece is pretty much all about the massive effect one person had on my life. Can one person predispose you to depression and PTSD? Probably not on their own. But when their behaviour is so outrageously unreasonable and the timing of some of it significant I believe it can. Actually not believe but know.
It is a person with whom I had a significant relationship several years ago. A very intense and initially apparently happy relationship. The wheels came off very badly in the end. The reason is no longer relevant. I think the initial action to cause it was her fault. She certainly hid something from me early on that, had she not, would have made things follow a completely different path. Impossible to say what that path might have been.
I knew she had a colourful past and on one occasion she flirted outrageously in front of me which tapped into my own insecurities. Had I been more mature I might have coped with that differently.
The upshot was that her various behaviours massively dented my self-esteem and I believe made me prone to the types of mental illness I later suffered from. It also affected deeply important friendships with mutual friends.