Evolutionary predisposition is the analysis du jour when describing all of human behaviour. These days everything we do--from appreciate music to donate to charity--evidently boils down to our desire to lure a mate and make many babies.

Now it seems a scientific study has proven an evolutionary reason for depression:

Dr [Randolph] Nesse’s hypothesis is that, as pain stops you doing damaging physical things, so low mood stops you doing damaging mental ones—in particular, pursuing unreachable goals. Pursuing such goals is a waste of energy and resources. Therefore, he argues, there is likely to be an evolved mechanism that identifies certain goals as unattainable and inhibits their pursuit—and he believes that low mood is at least part of that mechanism.

A study published this month in the Journal of Personality and Social Psychology suggests this clever idea might even be true.

Carsten Wrosch from Concordia University in Montreal and Gregory Miller of the University of British Columbia studied depression in [97] teenage girls... Their conclusion was that those who experienced mild depressive symptoms could, indeed, disengage more easily from unreachable goals. That supports Dr Nesse’s hypothesis. But the new study also found a remarkable corollary: those women who could disengage from the unattainable proved less likely to suffer more serious depression in the long run.

The conclusion to this study is that mild depression is in fact a healthy response to failure. The resulting decline in motivation then lets gloomy folks conserve energy and craft new goals. Disengaging early on saves people from feeling more severe depression down the road.

Adding injury to insult, Dr Wrosch published a paper in 2007 that found that guilelessly pursuing "unattainable" goals (ie, "following your dreams") is also bad for your health (something about concentrations of the inflammatory molecule C-reactive protein, naturally). 

It is often satisfying to learn of some sort of evolutionary reason for behaviour--particularly the otherwise odd or inscrutable kind. Philosophers and psychologists may chafe at such a tidy approach to analysing human activity, but it is usually reassuring to believe there is some sort of method to the madness.

This theory on depression, however, is uniquely depressing. How unfortunate to learn that it is in fact healthier to be unambitious, and that dogged ("boot-strap"?) persistence can lead to despair. This, evidently, is the reason why Americans suffer the highest depression rate in the world, Dr Nesse speculates. The problem is all those many goals.



Picture credit: fakelvis (via Flickr)