Jonah Lehrer argues in the New York Times Magazine that depression might be good for us. He's popularizing a theory advanced by two Virginia researchers who claim that depression is an adaptive mechanism that compels us to withdraw from the world and focus intently on our problems.
The fact that depression is so common strikes him as an evolutionary paradox. About 7 percent of adults will experience some depression in any given year, according to Lehrer's statistics. We know that at least some kinds depression have a heritable component, i.e., that genes help explain why depression strikes some and not others. At first glance, depression seems obviously detrimental to fitness. Every classic symptom seems to hurt a sufferer's chances of passing on her genes: Depression saps productivity and decreases mental accuity. Depressed people lose interest in food, socializing, and even sex. Depressed parents may struggle to care for their children. Hardly a recipe for fitness. So, why did such terrible genes persist?
But Lehrer thinks he sees a silver lining:
The alternative, of course, is that depression has a secret purpose and our medical interventions are making a bad situation even worse. Like a fever that helps the immune system fight off infection — increased body temperature sends white blood cells into overdrive — depression might be an unpleasant yet adaptive response to affliction. Maybe Darwin was right. We suffer — we suffer terribly — but we don’t suffer in vain.
Lehrer is arguing for an evolutionary take on the so-called analytical rumination model of depression.