Depressed people hurt others as well and say very painful things. I see it around me and I am not too sure trauma causes it since there are plenty of people with trauma doing great.
So it's character, DNA, hormones (a lack?) mixed with certain thoughts (thinkers and creative ones first?) that makes one sink out of the blue and shut out the world or something starts living it's own life steered by our thoughts.

I am sorry what you have to go through and it's more than just sadness or having a bad day. It's hard to stop drowning unless you live a very regular, healthy life, high dose of D3 might help, and you are alert if it comes to your feelings.

Depressions can be once or a lifetime. There are meds but if they all benefit. 🤔

A warm embrace to you. Know you are not alone.
🍀♥️