[snagglegaggle]

What would convince you? It should be pretty clear at this juncture I don't have evidence. However I did give a reason; if in general depressed people feel they are not contributing or participating in society then that is pretty clear.

You can look into this further: a lack of physical activity tends to worsen depression, and a hunter-gatherer with reduced mobility and/or other issues that make it hard to interact with the group is most certainly a resource drain. It goes on and on.

Evolution isn't directed but structures and instinct that are truly against the organisms interest are the exception, not the norm.