system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what are reasons for depression and how does it work?

I know it has something to do with serotonin, but that's pretty much all I know.
gpt
Its basically a lack of the happy chemicals in the brain. Sometimes theres reason for it like trauma and sometimes it just happens with seemingly no reason. Medication can help by making the body release more of the chemicals but therapy helps too. The act of talking about problems and getting it off your chest can help relief anxiety. Exercise helps because it releases the feel good hormones (like getting a runners high).