All true.
I just want to add that even though OP may see it in HN - that doesn't mean we have a higher-than-average depression rate. Every career will have a few depressed people, our community is online a lot though, so it's a natural place to ask for help.
HN's getting more of those posts partly because you can create a throwaway account easily, and also because HNers have been warm and understanding of posters who may be depressed. In other communities there's a greater chance of trolls and griefers replying with personal attacks or suggesting suicide.