Depression Defies the Rush to Find an Evolutionary Upside

By RICHARD A. FRIEDMAN, M.D.

In certain quarters of academia, it’s all the rage these days to view human behavior through the lens of evolutionary biology. What survival advantages, researchers ask, may lie hidden in our actions, even in our pathologies?

Depression has come in for particular scrutiny. Some evolutionary psychologists think this painful and often disabling disease conceals something positive. Most of us who treat patients vehemently disagree.

Consider a patient I saw not long ago, a 30-year-old woman whose husband had had an affair and left her. Within several weeks, she became despondent and socially isolated. She developed insomnia and started to ruminate constantly about what she might have done wrong.

An evolutionary psychologist might posit that my patient’s response has a certain logic. After all, she broke off her normal routine, isolated herself and tried to understand her abandonment and plan for the future. You might see a survival advantage in the ability of depressed people like her to rigidly and obsessively fix their attention on one problem, tuning out just about everything and everyone else around them.

Certain studies might seem to support this perspective. Paul W. Andrews, a psychologist at Virginia Commonwealth University, reported that normal subjects get sadder while trying to solve a demanding spatial pattern recognition test, suggesting that something about sadness might improve analytical reasoning.

In a similar vein, Joseph P. Forgas, a psychologist at the University of New South Wales in Australia, found that sad subjects were better judges of deception than happy ones. After subjects were shown a video intended to induce a happy or a sad mood, Dr. Forgas had them view deceptive or truthful interviews with people who denied committing a theft. Subjects in a sad mood were more skeptical and more accurate in detecting deceptive communication, while subjects in a positive mood were far more trusting and gullible.

Findings like these may suggest some benefits to sadness, but lately they have been generalized to patients with full-blown depression. For example, Dr. Andrews and Dr. J. Anderson Thomson Jr., a psychiatrist at the University of Virginia, have proposed that the rumination of depressives is an adaptive strategy to solve a painful problem. Clinicians, on the other hand, continue to maintain that the grim outlook of depressives is evidence that their thought process is distorted and erroneous. It must be fixed, not embraced.

There is strong evidence from neuropsychological and brain imaging studies that clinical depression is linked with various types of memory impairments in all age groups and at all levels of depressive severity. Challenging and changing the dysfunctional thoughts of depression are the exact aims of cognitive-behavioral therapy, one of the most empirically validated and popular forms of psychotherapy.

So who’s right about depression, the evolutionary biologists or the clinicians?

To start, the subjects in the above studies were normal controls whose moods were manipulated to be transiently sad. They do not really resemble people with clinical depression, whose condition can last months or even years.

Indeed, as Dr. Forgas said by e-mail, “I never worked with depressives, and I do not think that the experiments we have done looking at mood effects on cognitive processes in normal populations experiencing minor, everyday mood differences can be readily generalized to depressive cognition.”

Under close scrutiny, the case for depression’s adaptive benefits has problems — big ones. For one thing, the ruminative thinking of depression is often not particularly effective in solving problems. As another patient of mine once said: “I would think the same things over and over and could never decide what to do. It’s not a creative way of thinking.”

More critically, depression can arise without any psychosocial stressor at all, which makes it hard to argue that depression is a response to a difficult situation or problem. Dr. David J. Kupfer, a psychiatrist at the University of Pittsburgh, has found that a major life stressor almost always precedes a first episode of depression, but that episodes recur with milder stressors, or even none at all.

If depression conferred a problem-solving benefit, it should not become a chronic or autonomous condition — which it is for about half the patients.

According to the World Health Organization, depression is the leading cause of disability and the fourth leading contributor to the global burden of disease, projected to reach second place by 2020. There is also strong evidence that it is an independent risk factor for heart disease, and several studies show that prolonged depression is associated with selective and possibly permanent damage to the hippocampus, a region of the brain critical to memory and learning.

Add the fact that 2 percent to 12 percent of depressed people eventually commit suicide, and the “advantages” of depression suddenly don’t look so good.

Why, then, does the notion persist that depression confers special insights and benefits?

I got a clue recently from one depressed patient. He was an educated and articulate young man, unhappy because the world was such an awful place, he said. Because he had so many other symptoms of depression — insomnia, fatigue, low libido and poor self-esteem — I told him that he was clinically depressed and that his Hobbesian worldview was probably a result of depression, not its cause.

He scoffed, but he was willing to try a course of cognitive-behavioral therapy and antidepressant medication, if only to feel better. Months later, when he had recovered, I asked him again about his worldview.

The world was just as dire, he said, but he felt better. Still, he speculated wistfully that his newfound cheerfulness was not his authentic self, which he described as brooding and creative.

This cuts to the heart of why depression is increasingly romanticized. What is natural, the thinking goes, is best. If we are designed to suffer depression in response to life’s ills, there must be a good reason for it, and we should allow it to take its painful and natural course.

But unlike ordinary sadness, the natural course of depression can be devastating and lethal. And while sadness is useful, clinical depression signals a failure to adapt to stress or loss, because it impairs a person’s ability to solve the very dilemmas that triggered it.

Even if depression is “natural” and evolved from an emotional state that might once have given us some advantage, that doesn’t make it any more desirable than other maladies. Nature offers us

, infections and heart disease, which we happily avoid and do our best to treat. Depression is no different.