If depression has an evolutionary purpose, it's certainly not obvious. Depression makes people consider suicide and less interested in sex, which does not encourage the species' survival. But two evolutionary psychologists theorize that depression's purpose is enhanced mental skills.
Photo by kevindooley.
Sadness focuses the brain's attention on a conflict, and makes you better-equipped to make good decisions.
A fascinating New York Times magazine article entitled Depression's Upside explains that the ventrolateral prefrontal cortex (VLPFC) is the part of our brain that controls what we pay attention to.
Several studies found an increase in brain activity (as measured indirectly by blood flow) in the VLPFC of depressed patients. Most recently, a paper to be published next month by neuroscientists in China found a spike in "functional connectivity" between the lateral prefrontal cortex and other parts of the brain in depressed patients, with more severe depressions leading to more prefrontal activity. One explanation for this finding is that the hyperactive VLPFC underlies rumination, allowing people to stay focused on their problem. [...] Human attention is a scarce resource - the neural effects of depression make sure the resource is efficiently allocated.
Therefore, when you're depressed, your brain kicks into total-focus mode, and sets you into a cycle of rumination on the problem at hand.
The downcast mood and activation of the VLPFC are part of a "coordinated system" that, Andrews and Thomson say, exists "for the specific purpose of effectively analyzing the complex life problem that triggered the depression." If depression didn't exist - if we didn't react to stress and trauma with endless ruminations - then we would be less likely to solve our predicaments. Wisdom isn't cheap, and we pay for it with pain.
Not everyone agrees with the positive spin on why depression exists, mostly because there are so many different types of depression—some triggered by events and problems, and others that persist for years without an obvious cause.
Ed Hagen, an anthropologist at Washington State University who is working on a book with Andrews, says that while the analytic-rumination hypothesis has persuaded him that some depressive symptoms might improve problem-solving skills, he remains unconvinced that it is a sufficient explanation for depression. "Individuals with major depression often don't groom, bathe and sometimes don't even use the toilet," Hagen says. They also significantly "reduce investment in child care," which could have detrimental effects on the survival of offspring. The steep fitness costs of these behaviors, Hagen says, would not be offset by "more uninterrupted time to think.
Still, those who suffer from depression do get the benefits of enhanced mental skills.
Joe Forgas, a social psychologist at the University of New South Wales in Australia, has repeatedly demonstrated in experiments that negative moods lead to better decisions in complex situations. The reason, Forgas suggests, is rooted in the intertwined nature of mood and cognition: sadness promotes "information-processing strategies best suited to dealing with more-demanding situations." This helps explain why test subjects who are melancholy - Forgas induces the mood with a short film about death and cancer - are better at judging the accuracy of rumors and recalling past events; they're also much less likely to stereotype strangers.
These mental boosts are often responsible for quality creative output.
In a survey led by the neuroscientist Nancy Andreasen, 30 writers from the Iowa Writers' Workshop were interviewed about their mental history. Eighty percent of the writers met the formal diagnostic criteria for some form of depression. A similar theme emerged from biographical studies of British writers and artists by Kay Redfield Jamison, a professor of psychiatry at Johns Hopkins, who found that
successful individuals were eight times as likely as people in the general population to suffer from major depressive illness.
(Emphasis mine.)
Even though I quoted it at length, this whole article is worth the read, especially for folks who tend toward depression. Knowing about the ways sadness can benefit you just might make you feel a little better.
The Evolutionary Reason for Depression [Smarterware]
Depression's Upside [NYT via]
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