The Benefits of Depression: Boosting Brain Power?

Jonah Lehrer's piece "Depression's Upside" opens with Charles Darwin, a man who had an entire vocabulary for his own suffering. The Victorians used many terms for depression, and Darwin reached for all of them. He catalogued his "fits," set off by "excitements," the "flurries" that brought on an "uncomfortable palpitation of the heart," the "air fatigues" that triggered what he called his "head symptoms." In one letter to a doctor who practiced "psychological medicine," he admitted to "extreme spasmodic daily and nightly flatulence" and to "hysterical crying" that overtook him whenever his wife, Emma, stepped out and left him by himself.

What bothered Darwin most was the recurrence of it. There were stretches when he could not work one day out of every three, and he wrote of choking on his "bitter mortification." He saw a weakness of mind running through his family and did not expect to beat it. "The 'race is for the strong,'" he wrote, and figured he would do little more than admire the progress others made in science.

What actually happened looks almost like the opposite. Darwin seems to have turned his symptoms into a reason to disappear into his research. "Work is the only thing which makes life endurable to me," he said, and years later called it his "sole enjoyment in life." The low moods pulled his attention inward and held it there. In his autobiography he tried to reason out what all that misery was for, and his own biography kept bleeding into his theory. Pain or suffering of any kind, he reasoned, if it goes on long enough, produces depression and weakens the capacity to act, yet it is well suited to make a creature guard itself against sudden harm. Pleasure, in other words, was not a complete enough account. Sometimes the sadness itself does the informing, steering an animal toward the course of action that will do it the most good.

Most mental illnesses are rare. Schizophrenia turns up in fewer than one in a hundred people. Depression is different. It is as ordinary as a head cold, and the figure usually cited is that somewhere between 7 and 10 percent of people will carry some degree of it. That ubiquity, Lehrer notes, was a problem for Darwin's own framework. If depression is simply a malfunction, then evolution blundered badly, letting an affliction that works against reproduction (it drives people away from sex and toward thoughts of suicide) spread through the whole species. By that reading the modern mind tilts toward sorrow for no good reason and has to be medicated back out of it.

Lehrer asks whether the sheer commonness of depression might be pointing at something else. What if the condition has a function we have not identified, and what if our medicines and treatments are cutting across an adaptation rather than correcting a flaw?

To chase that question he spent time with Andy Thomson, a psychiatrist who has run a private practice in Charlottesville for 32 years and teaches at the University of Virginia. Thomson has a scruffy gray beard and sharp cheekbones, and when he talks he tends to shut his eyes, as though he has to shut out everything else to find the words. Mostly, though, he listens. "I tend to get the real hard cases," he told Lehrer. Many of his patients have already cycled through several treatments and show up with little hope left. During one of the winter days Lehrer watched him work, Thomson kept glancing at his phone. A patient on "welfare watch," required to check in regularly, had gone quiet, and it worried him. "I've never gotten used to treating patients in mental pain," Thomson said. You see one case of iron-deficiency anemia, he explained, and you have basically seen them all; but every person who walks into his office is hurting for a reason that belongs only to them.

Thomson had gotten interested in evolutionary psychology and how the brain evolved back in the late 1990s. In 2004 he met Paul Andrews, an evolutionary psychologist at Virginia Commonwealth University who had been circling the same puzzle for years: why does a disorder this costly stay this common? The two of them started with the mental process at the center of depression, the one called rumination.

For a long time psychiatry has treated rumination as a bad habit of the mind. The brain keeps circling back to a person's flaws and troubles, and each pass deepens the gloom. Intrusive negative thoughts arrive, and they feed the symptoms that produced them. The Yale psychologist Susan Nolen-Hoeksema has shown that people with "ruminative tendencies" are more likely to slide into depression and more likely to be thrown by stress. After the 1989 Loma Prieta earthquake, she found that San Francisco residents who described themselves as ruminators reported markedly more depressive symptoms than those who did not.

Then there is the cost to thinking. Because rumination seizes the stream of consciousness and makes a person acutely attentive to their own pain, study after study has found that depressed people have trouble holding anything else in mind. They do poorly on tests of memory and executive function, especially when there is a lot of information to juggle. Those gaps close, notably, when subjects are first pulled away from their low mood and can give the task their attention. All of which seemed to confirm that rumination is just pessimism spinning in place, a drain on mental energy with nothing to show for it.

Andrews and Thomson looked at the same thing and saw a question instead of a verdict. Rumination, they agreed, usually follows a real blow: a death, a lost job. Darwin himself fell into a crushing grief after his ten-year-old daughter Annie died of complications from scarlet fever. "It's usually a response to something real, a real setback," Andrews said. It struck him as odd that the brain would short-circuit at exactly the moment a person needs it most.

Lehrer walks through an example to make the idea concrete. Picture someone sunk into depression by an ugly divorce. The ruminating might show up as regret ("I should have been a better spouse"), as replayed alternatives ("What if I hadn't had the affair?"), as dread about what comes next ("How will the kids handle it? Can I cover the alimony?"). Therapists try to break that cycle because it keeps the depression going. But Andrews and Thomson wondered whether the same grinding might also be rehearsing a person for what lies ahead, or letting them extract a lesson from the wreckage. "I started thinking about how, even if you are depressed for a few months, the depression might be worth it if it helps you better understand social relationships," Andrews said. Maybe the person comes out of it realizing they need to loosen up, or soften. Insights like that can be worth a great deal, and they can be exactly what depression hands over.

Their proposal, then, ran against the standard one. Rumination, they argued, might produce better outcomes, particularly on the hardest problems a life throws up. They paid attention to the core symptoms themselves: the drop in pleasure, the shift in eating, the fading interest in sex and in other people. To Andrews and Thomson, the point of those symptoms was that they "reduced the possibility of becoming distracted from the pressing problem." The whole system seemed built to clear the field so one difficult thing could be worked on without interruption.

They traced that capacity for narrow, sustained focus to a specific patch of the brain, the left ventrolateral prefrontal cortex, or VLPFC, sitting a couple of inches back from the forehead. The region has been tied to a grab bag of abilities, from conceptual knowledge to conjugating verbs, but it looks especially important for keeping attention fixed. Experiments show its neurons have to keep firing to hold us on task, so that stray information does not pull us off course. Damage or deficits in the VLPFC, meanwhile, have turned up in connection with attention-deficit disorder.