Point taken, but I'd argue that those people who manage to work 9-5 for extended periods of time are, first, probably not suffering from severe depression, and

Point taken, but I'd argue that those people who manage to work 9-5 for extended periods of time are, first, probably not suffering from severe depression, and second are actually participating in on-the-job learning that really adds up over the years. If you have severe depression, you are probably going to be missing out on years (or even decades) of work, and not learning nearly as much either on or off the job... or at most learning a bit on the rebound from your depression (as it's often cyclical, and even severely depressed people tend to have better days when they feel at least somewhat motivated or at least manage to keep it together). Such severely depressed people are just not going to be competitive with people who manage to keep on working 9-5 for most of their career, even if the latter put in zero extra effort to learn outside of work.