[delackner]

You may be right, but there's an alternative explanation that would make both your perspective and the article's theory hold. You chose the word "function" to describe how you feel. Functioning means I suppose meeting the expectations (both internally and externally imposed) in the society you are in, in the activities that you engage in, in the roles and relationships (personal and professional) that you are connected to.

If any those connections seemed to be wrong for you, but you were unable to see an alternative, wouldn't depression in the sense of the article be a good way for your body to try to devote lots of energy to finding an alternative?

Maybe a world with such tangled and deep functional requirements implies that in some cases the "solution" that depression tries to help you find, might not always exist. Or might require such a huge allocation of effort that one alternative - ignoring the dissatisfaction - becomes attractive.