I don't know if any one thing "caused" it. A lot has happened in my life that has contributed, but as far as cause goes? I think I was just predisposed, to be honest. They say people who grow up with parents who struggle are more likely to struggle themselves. My mom has alcoholism, depression, and an adjustment disorder. So, it's not too surprising that I have depression. I do think circumstances have contributed, though.

Wasted potential, for example. I used to be in the Beta Club. If I had actually kept up with my schoolwork, I could have gotten a scholarship. I used to want to go to Harvard. You know? Not a day goes by where I don't think about that, and regret it. But why did I waste said potential? Depression. So, that wasn't the cause, obviously. Abuse, isolation, poverty, etc. They all contributed. But none caused it, only made it worse.

I don't recall a single trauma that did cause it. To be frank, I remember being depressed even as a child.

ETA: I have heard postpartum depression in either parent can contribute to depression later in the child's life. I really hope it doesn't in the case of my baby.