Depressed people - what is their problem? Edward Hagen of Humboldt University has a fascinating answer: Getting depressed is a good way to get the people around you to give you more for less. Feel underappreciated? Then mope around non-stop, and the people who depend on you will pick up the slack. Hagen explains it with a tidy economic metaphor:
Given that the principal cause of major unipolar depression is a significant negative life event, and that its characteristic symptom is a loss of interest in virtually all activities, it is possible that this syndrome functions somewhat like a labor strike. (emphasis mine)
The idea is that during humans' evolutionary history (and even today, inside the family), you couldn't easily hire a replacement for a malcontent:
It would have been difficult, for example, for mothers to raise offspring without help from the father and/or other family members; conversely, the fitness of the father, parents, and other family members depended critically on the mother successfully raising offspring. Abandonment of one party by another would have entailed a significant fitness cost to all...
In evolutionary terms, then, getting depressed is basically a way of saying: "Treat me better, or you'll have to get by without my help." According to Hagen, it usually works:
A number of behavioral studies have demonstrated that although depression in one family member prompts negative feelings from other family members, it nonetheless appears to deter their aggressive behavior and to cause an increase in their tendency to offer solutions to problems in a positive or neutral tone and an increase in their solicitous behavior (e.g., caring statements), consistent with the bargaining model.
Post-partem depression is a case in point:
[T]he spouses of individuals experiencing PPD should report increasing their investment in parenting, and in fact they do. Depression scores for one spouse were positively correlated with reports of increasing investment in childcare by the other spouse (Hagen 2002). High levels of help from spouses and better interactions with infants in one study were also the only variables associated with remission of PPD...
How can suicide be functional? It can't be. But suicide threats can be highly functional:
Suicide permanently removes oneself as a source of valuable benefits for the group. Suicide threats are therefore threats to impose substantial costs on group members and can be viewed as a means to signal cheaply and efficiently to a large social group that it may suffer such costs if assistance or change is not forthcoming. Suicide attempts are necessary to underwrite the credibility of suicide threats and must therefore entail a genuine risk of serious injury or death.
Need I point out how Szaszian this "bargaining model of depression" is? Hagen doesn't cite Szasz. But it would be easy to sum up his paper with a Szaszish aphorism: "They're not depressed; they're depressing!"