In yesterday’s post I laid out an adaptive hypothesis for the evolution of depression — a hypothesis presented in two new papers by Andrews and Thompson. In short, their “analytical rumination hypothesis” (ARH) proposes that the “malady” we call depression is actually an adaptive behavior built into our ancestors by natural selection. When facing difficult social problems, selection is said to have promoted behaviors that make individuals withdraw from life, ceasing to engage in formerly pleasurable activities like socializing, eating, and sex. This is all in the service of rumination: freed from other activities and commitments, the depressed individual is said to analyze the problems that led to depression in the first place, eventually solving them and re-entering society. This is “adaptive” because individuals who lacked the depressive syndrome would not be able to solve their life problems so easily, and would leave fewer offspring than individuals who shut down and ruminated. In such a way the genes promoting depression increased in our ancestors.
The ARH involves more than just the above, including a hypothesis about the biochemical basis of depression, which involves an excess of the neurotransmitter serotonin. Do consult the original paper if you want more details. I also described why the authors saw depression as an adaptation. Their rationale is quite weak — in essence consisting only of a story of how analytical rumination might have been adaptive in our ancestors. The authors give no cost-benefit analysis for depression, despite the fact that the costs are certainly severe. At present they include an appreciable frequency of suicide. And, as one alert reader pointed out, a loss of appetite or desire for sex would have been seriously maladaptive in our savanna-dwelling ancestors. Imagine an ancestral H. erectus, curled up on the floor of his cave, ruminating obsessively because he suspects his mate of infidelity. He doesn’t sleep; he doesn’t eat; he doesn’t have sex or go hunting with his mates. Does this really give him an adaptive advantage? This scenario is a bit facetious, but the point is serious.
Today I want to briefly examine the evidence proffered by Andrews and Thomson in support of the ARH. I’ll break it down into a series of questions.
Is depression caused by difficult social problems ? On this crucial point the authors give virtually no evidence. [NOTE: It's since been called to my attention that there is work suggesting some association between depression and difficult life situations. Again, however, there is a cause-and-effect problem here: people with a tendency to be depressed may more often get themselves into difficult life situations.] People who have experience depression often say that its onset is often mysterious, not associated with an identifiable problem (see, for example, some of the commenters on yesterday’s post). But the authors wave that difficulty away: “Many people may be reluctant to disclose the reasons for their depression because the problem is embarrassing, reputationally damaging or otherwise insensitive, which is often why depressive episodes may appear to be endogenous. . .” This is almost Freudian in its hauteur. Here the authors presume that there is a social reason for depression rather than treating it as a hypothesis.
The authors do note that “interpersonal conflict is commonly associated with depression. . “. One example is that “in married couples, the risk for major depression is about 40 times greater if the couple is unhappily married.” Well, you can see the problems with this: what is the cause, and what the consequence? Perhaps the social problems result from undiagnosed depression. It’s easy to see that being married to someone with incipient or undiagnosed depression could cause unhappiness. Depressed people are often hard to get along with.
Does depression enhance analytical rumination? Again, the evidence is very, very weak. The authors cite only one “pertinent mood induction experiment”, which may not be relevant at all. In this experiment participants (finance and economics students) were offered the chance to buy and sell German marks and Swiss francs (this was before the Euro in Germany), and were given historical information about markets that could help them with their decision. Success was judged by how much profit was made.
The authors of this study (Au et al. 2003) supposedly created depression-istic conditions in the participants in this way:
Mood was manipulated by providing participants with false feedback on the first round. In the positive mood induction, participants received a high profit for their decision, regardless of what they actually did. In the sad mood induction, participants took a substantial loss. In the neutral mood induction, participants broke even. For all subsequent rounds, participants’ payoffs were determined by their actual decisions and mood was maintained with positive music, sad music, or no music.
Here’s Andrews’ and Thomson’s analysis:
People in positive moods made worse decisions by both standards: They were less accurate, and they lost more because they invested more. Sad participants made the most accurate decisions, but they tended to invest conservatively. Neutral participants were not as accurate as sad participants, but they received a higher profit because they invested more.
This experiment is very much in line with a model of depression’s causes and cognitive effects suggested by Gifford Weary and her colleagues (Weary et al., 1993). Participants experienced an increase in sad affect when they received feedback that their causal understanding of their situation (the trading situation) was
erroneous or in need of modification. Sad affect appeared to have focused their attention on the problem and helped them analyze it so that they could gain control over the situation.
Only in evolutionary psychiatry could a study like this count as “evidence” for the ARH. All it says to me is that if you lose your shirt when engaging in a financial speculation, you tend to be more cautious. If you gain a lot, you tend to be euphoric and not as cautious. Surprise! What this has to do with clinical depression is a mystery.
Does depression help people solve their social dilemmas? The authors cite some studies that, they say, support this contention (see p. 634 of the Psychological Review paper). The one they describe in detail, however, doesn’t inspire much confidence.
In this study pairs of participants played “Prisoner’s Dilemma”. There were three kinds of pairs: depressed people paired with nondepressed people, nondepressed people paired with other nondepressed people, nondepressed people paired with people with “other problems” (e.g. high “fear” tendencies). “High power” participants were those who made the first choice in the dilemma, “low power” participants went second. Overall, depressed people scored marginally better than “normals”, but the difference isn’t impressive: 97.4 versus 88.5 points, a difference that isn’t reported as statistically significant. Andrews and Thomson impute the results to the fact that “the behavior of the depressed participants was more sensitive to position. In the high power position, depressed participants tended to defect more; when in the low power position, they tended to cooperate more.
Well, this may be relevant to the problem, but as a strong piece of evidence for depression helping solve thorny social dilemmas, it’s weak. It’s certainly not enough evidence to tell people to go off their meds! Ideally we’d like to examine two groups of people that face similar social dilemmas, such as infidelity. One group would consist of those who experience post-dilemma depression, the other would not. Psychologists could then assay whether the depressives had more positive outcomes.
The authors cite one more bit of evidence for the use of depression to solve dilemmas:
That depression may help people solve social dilemmas is also supported by research on real-life dilemmas. When in conflict with close, cooperative social partners, people tend to show more sympathy, more support, and reduced aggression when their partner has depressive symptoms . The supportive response that depressed people get from their close social partners has led some researchers to argue that it reinforces depressive tendencies, which suggests that it may be useful in solving social dilemmas. [References omitted; see original paper.]
Well, this does bespeak the milk of human kindess,but it’s not clear whether sympathy does reinforce depressive tendencies (which the authors see as good), and even less clear that “more sympathy and support” translates into “solved social dilemmas.”
Such is the nature of the evidence in evolutionary psychiatry: tendentious, thin, and highly speculative. I’m used to that, but not to the prescription that doctors do away with antidepressants:
Our review suggests that medications treat symptoms, whereas psychotherapies are more likely to be treating cause. The analytical rumination hypothesis suggests that psychotherapies are productive when they help depressed people identify and solve important problems in their lives. It also suggests that depressive rumination is useful and that antidepressants may interfere with the ability to ruminate. For these reasons, the analytical rumination hypothesis would place greater emphasis on psychotherapy and less on medications.
The authors suggest that “problem-solving” forms of psychotherapy, like cognitive behavioral therapy (CBT) will be more useful, since they concentrate on having the depressed person solve problems. I’m not that familiar with CBT, so I don’t know whether the “problems” it helps solve are those identified as precipitating depression in the first place, but data do show that it seems to be effective. But no more effective than drugs. The most enlightened treatment of psychiatry today appears to be a combination of psychotherapy and medication. Before we do away with the latter, we’ll need a lot better analysis than that of Andrews and Thompson.
It may be worth mentioning here that if depression helps you solve life problems, one episode apparently doesn’t do the job. If you’ve had a major depression, the probability that you’ll have another within five years is nearly 80%. This suggests that the condition is a chronic pathology, although of course Andrews and Thompson might respond that this may just reflect genetic differences between people (but then why aren’t “depression genes” fixed in all humans?), or that some people just have a lot of problems and need to experience recurrent adaptive depressions.
Worthwhile books on depression:
There are two superb accounts of depression, both written from the inside, that show the “adaptation” in all its frightening intensity. One is embryologist Lewis Wolpert’s personal/scientific account, Malignant Sadness: The Anatomy of Depression. The other is author William Styron’s account of his “adaptation,” Darkness Visible: A Memoir of Madness.
Manic depression is not the same clinical syndrome as depression, but I thought I’d include the following for general interest:
An Unquiet Mind: A Memoir of Moods and Madness and Touched With Fire: Manic-Depressive Illness and the Artistic Temperament, by Kay Redfield Jameson. Jameson is a clinical psychologist and a superb writer, who also suffers from severe manic depression. She’s written an engrossing memoir of her illness (now under control with lithium), which shows the difficulty that even a trained mental-health worker has with staying on medication. Her Touched with Fire is interesting, maintaining as it does that manic depression may be closely connected with artistic genius. She may well be right, though the book suffers a bit from making a virtue of necessity.