[wvh]

You just described causes of depression, like divorce, social isolation and being unemployed. I know there are people that can feel free in a place as horrible as a concentration camp, but most of us have some basic needs that have to be met to feel OK and have some hope.

Some people have actual neurotransmitter imbalances, but many of us just have monkey brains that don't know how to deal with (real, abstract) modern-day stressors that trigger a fight-or-flight response.