Perhaps a better way of phrasing this is: suffering from depression? Don't do that startup unless you have a safety net (of course, that could apply to people without depression too). Hell, I'd say that applies to doing a PhD (I'm in one right now) or anything that does mean you have to deal with a lot of ambiguity on your own. In those situations it's all too easy for even the most mentally secure person to start neglecting themselves in the service of the work (mentally, emotionally, psychologically, physically), potentially to disastrous effects.