With major depression, you can’t sleep, don’t eat, and might not even get out of bed. In the worst case, it leads to suicide. It hardly seems like a recipe for thriving and reproducing. So why does it persist in the human population?
Jonah Lehrer (author of How We Decide) writes in the New York Times on the “analytical rumination hypothesis” (ARH) that says depression allows people to solve difficult problems through sustained contemplation.
The article offered competing evolutionary explanations for depression: “plea for help” where depression encourages loved ones to assist the depressed person; “signal of defeat,” in which depression reduces potential for social conflict; and “depressive realism,” which says that people with depressed outlooks have a more accurate understanding of what’s really going on. The ARH doesn’t seem as plausible as these other theories.
I want to dig into a second, related claim reported by Lehrer, that depressed affect (not major depression, but merely a negative, ruminative mindset) is associated with more analytical (hence better?) cognitive functioning:
It doesn’t matter if we’re working on a mathematical equation or working through a broken heart: the anatomy of focus is inseparable from the anatomy of melancholy. This suggests that depressive disorder is an extreme form of an ordinary thought process, part of the dismal machinery that draws us toward our problems, like a magnet to metal.
But is that closeness effective? Does the despondency help us solve anything? Andrews found a significant correlation between depressed affect and individual performance on the intelligence test, at least once the subjects were distracted from their pain: lower moods were associated with higher scores. “The results were clear,” Andrews says. “Depressed affect made people think better.”
You mean when I’m obsessing over something I’m better able to do math? Sounds great. But I’m skeptical.
What does the research really say?
The paper reporting these findings (Andrews & Thomson, 2009) identifies competing threads in the research literature. One thread suggests that “depressed affect is associated with and causes performance decrements in a variety of cognitive domains, including memory, intelligence, and executive functioning.” The other suggests that “depressed affect promotes an analytical processing style that enhances accuracy on complex tasks.”
In my quick reading of the paper, I didn’t see any cited research showing that depressed people do better at math. They cited studies showing that depressed people may be better at judgment of control (perceiving correctly how little or much control they had over lighting a light bulb, for example), mindreading (when it requires some level of analysis), and making rational decisions (e.g., around monetary decisions).
Here’s related research reported in the New Scientist saying much the same thing: grumpy people think better. Yes, there is probably a U-shaped curve. You can’t do math when you’re hypomanic because the birds are singing! the sun is shining! who cares about math! On the other hand, you can’t do it when you’re clinically depressed either, because you’re either asleep in bed (at one in the afternoon) or awake in bed (at one in the morning). There’s some optimum — is it at some subclinically depressed, slightly obsessed state? I doubt it.
The relationship between depression and intellectual focus
Obsessing over a math problem and obsessing over a person may use similar mental circuitry, I will grant you that. But a person caught up in working through a broken heart doesn’t have the mental resources to concentrate on a set of mathematical equations. There may be some correlation in a person’s ability to focus on math and their likelihood to get caught in negative rumination. This does not mean we should encourage negative rumination. Instead, we should help people stuck in it break free so they can use that mental focus in more productive ways.
There may well be a correlation between depressed affect and ability to focus on complex, analytical problems. This doesn’t mean, however, that the depressed affect is necessary for the focus. It is likely a hindrance.
Andrews said, “Depressed affect made people think better” but only once they were distracted from their pain. You would see this same result if people who naturally “think better” (i.e., more analytically and obsessively which may not always be better) also are more likely to have depressed affect. Those two things may go together, but not in the causal relationship depression –> intellectual focus.
In fact, they probably do go together. Autistic spectrum disorders, unusual intellectual achievement, and major affective disorder are often found in the same families. Autism manifests as an extreme ability to focus, to the exclusion of normal socializing or other behaviors. Depression is more likely to occur in people who ruminate obsessively. Intellectual achievement requires its own kind of obsessive rumination.
Depression itself may have some sort of evolutionary upside — but any enhanced mental functioning is not due to depression but perhaps to an unusual ability to focus. I might rather call it a “necessity to focus” because it’s not always under a person’s control.
Andrews, P., & Thomson, J. (2009). The bright side of being blue: Depression as an adaptation for analyzing complex problems. Psychological Review, 116 (3), 620-654