Is depression an evolutionary adaptation? Part 2.

August 30, 2009 • 9:34 am

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.


Andrews, P. W. and J. A. Thomson, Jr. 2009.  The bright side of being blue: Depression as an adaptation for analyzing complex problems.  Psychological Review 116(3), 620-654.
Andrews, P. W. and J. A. Thomson, Jr. 2009.  Depression’s evolutionary roots. Scientific American, Aug. 25.

32 thoughts on “Is depression an evolutionary adaptation? Part 2.

  1. From my experience in MHSP settings you are correct. In no particular order, depression results when a reduction in norepinephrine/serotonin combined with psychic colonization brought about by anxiety (anxiety is its close compadre) or excessive stress become predominant. I think the depression itself is not an adaptation, but how one overcomes it is (plasticity rather than problem solving). The CBT component relies on cognitive homework to practice correct processing of events in an attempt to alleviate or prevent future wallowing in the mire.

    1. JD, I just do not understand what you wrote here. Can you elaborate so that a layperson like me can understand?

      1. Depression can be seen as an ad hoc opportunity for the brain to “adapt” (with only an ephemeral, instrumental value)…but not in a way that benefits the species as an overall evolutionary adaptation. Depression itself is a lousy defense mechanism. Again, this is still speculative (psychology is more art than science) but the empirical evidence for cognitive behavior therapy is overwhelming, thus suggesting neurological plasticity plays a huge part in reversing chemical activity. This would also be, I’m assuming, Ramachandran’s view.

        Hope this makes a bit more sense.

        MHSP (mental health service provider).

  2. You’ve got it backwards on serotonin. Depression is associated with lower levels, not higher.

    Antidepressant drugs boost serotonin levels, through at least four different mechanisms, depending on the class of the drug.

    1. I am presenting the authors’ hypothesis, which, as I said yesterday, is that depression is associated with HIGH serotonin levels. And I pointed out that this is contrary to most opinion.

  3. Boy – the more one thinks about it, the weirder it seems. It’s as if A&T are doing a thought experiment with no relation to reality. In the real world, depression just isn’t like that. In the abstract it may seem that you can withdraw from ordinary activities in order to think better – and you can if you do it as it were voluntarily, i.e. from a decent baseline mental state or mood. But a withdrawal forced by depression is a withdrawal from everything including useful rumination! Who doesn’t know that?! Depression doesn’t just cause cognitive distortion, it IS cognitive distortion.

    1. That’s what is so weird about this paper — if I’m having a depressive episode, I’m sure as hell not ruminating, except possibly about different ways to kill myself. How can this possibly be an adaption?

  4. Does depression enhance analytical rumination?

    Speaking from personal experience, I would say no.

    I once had the idea that I would do better elsewhere than in the job I had. I made a rash statement about wanting out, and they obliged.

    Lets just say that was a rough time. My opportunity to “ruminate” certainly did not help me find something else. In fact, it made it damn near impossible. I had to go back, hat in hand, and beg for my former position back. (fortunately, they wanted me back. I was opinionated, but very competent.)

  5. Depression and suicide in men who (for instance) lose their jobs is adaptive for the group, if not the individual. The urge to self-preservation is so strong that it takes a considerable process to dismantle it so that an individual can cease being a burden on the group. The process is depression.

    1. Even if it worked that way, very depressed individuals would not propagate their genes and the effect would be lost.

      A more convincing explanation like that could be that some unspecified set of adaptations gauges an individual’s behavior according to his/her rank or circumstance in a social hierarchy. In the bell-curve of psychological well-being, from very good to very poor, depression might simply represent the very poor end. And it could be a result of those unspecified adaptations I mentioned above – gone “haywire”.

  6. I’m guessing these guys haven’t been depressed themselves. Of course I haven’t read all the stories in the world, but the ones I have read agree with my own experience. If depression was for useful rumination, I should have solved world hunger by now. Instead I think about endless variations of how useless and worthless I am and wonder how my cat would do without me (it’s usually the cat that keeps me here). I have not once solved a problem this way, and instead have acquired more problems.

    In some of this stuff it almost seems like they mean depression the way the layman often uses it (a very short term somewhat lowered mood due to some minor event). If they did, I could almost see their point, but obviously being in their field they ought to know better than to use a specific term like that.

  7. An excellent dissection. I wonder if they’re aware of how long Darwin waited after the Beagle voyage before publishing Origin?

  8. I always hated how that though, evolution ultimately aims to explain all structures, physiological functions, behaviors, an adaptive and somewhat plausible conjecture somehow seems to persist in evolutionary thinking.

    There’s many constraints and by products that we already know about. Others, as donald rumsfeld would say are “known unknowns”

    This is a area of active research.

    Yet at the same time I don’t like how Gould and others presented their backlash against adaptationism. While that was being said there were people who actually did do the footwork to verify specific predictions of adaptive hypotheses.

    Perhaps Gould’s position was necessarily extremist. Adaptationism for some reason still pervades even the learned biologists and related scholars.

    Just because something has a function, it doesn’t mean it came about for that reason.

  9. To add to what Ophelia, Fraser and BaldApe noted, depression is not typically associated with productive rumination. Don’t take my word for it, of course, look at the international criteria for the very diagnosis of a major depressive episode. Amongst them:

    “A person … reports that his/her ability to think, concentrate, or make decisions becomes impaired. Memory and distraction problems are common. This problem can be notably pronounced, causing significant difficulty in functioning for those involved in intellectually demanding activities.”


  10. I agree with this critique. I doubt depression enhances analytical rumination. (Maybe a very transient low mood does, but that’s a far cry from depression.) And I don’t think depression generally helps people to solve social problems.

    This was a very interesting critique, from which I learned a great deal. However, I have some criticisms and some ideas to bounce back.

    About “adaptation”:

    It seems like you are opposed to the idea that depression is adaptive or functional. But in some sense, isn’t it fairly obvious that depression is adaptive? – That genes with linkages to depression (the depression genotype) are selected for/against, and depression (the phenotype) affects this process.

    I agree that the papers you critiqued seemed to have a more specific/strict definition of ‘adaptation’, according to which you rightly criticized their conclusions.

    You made the point that it is not adaptive for a hunter-gatherer to lay on the ground ruminating over his mate’s possible infidelity – that obviously doesn’t help propagate his genes. I’d like to make an analogous point: according to the very loose definition of adaptation I alluded to in my above paragraphs, even heart attacks could be considered “adaptive”. Obviously a heart-attack won’t help me to propagate my genes. But there is a major difference between heart-attacks and depression: Heart-attacks are a terminal phenomenon most common in males past their most fertile years, but depression has linkages with many very obviously adaptive (in the strict sense) phenomena that affect reproductive success.

    I quote you about Andrews’ and Thomson’s analysis about depression and analytical rumination:
    “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.”

    I agree with your statement. It makes sense to me that depression does *not* cleanly alter one’s cognitive performance to an individual’s reproductive advantage. But it could be a “byproduct” or “spandrel” of some highly adaptive ‘adaptation’ (in the strict sense, meaning something with a clear function which improves gene propagation). Maybe depression is the result of an adaptation for risk avoidance, where the system goes haywire.

    Obviously depression is something to fix, it is not a good thing to be depressed. At the same time, it seems like there are strong grounds for a genetically adaptive, socially functional explanation of depression. That does not mean that it is ever an advantage to be depressed.

    I wonder if the disease model ever gets in the way of scientific inquiry. It seems like most people can’t distinguish the promising evolutionary explanations of depression from the “just so” stories – loose, unsound evolutionary hypotheses that praise the status quo or dismiss suffering. That makes it more difficult to make inquiries about adaptive explanations of depression.

    I would be interested in your opinion of the social rank theory of depression.

  11. In the book by Williams & Nesse on evolutionary medicine, they say a bit about depression. They take a very broad perspective on the pay-off between energy expenditure and conservation.

    They suggest one question for depressive clients should be about the goals they have set themselves. Any glaringly over-ambitious goals could be revised.

    It’s really just a fairly obvious but easily overlooked point, which became clearer for them after considering the evolution of the nevous system.

  12. I’ve been receiving treatment for dysthymia (a form of depression) and social anxiety for a while now. While it’s true that these conditions cause me to withdraw from social situations and ruminate, it’s hardly ever the case that these ruminations are productive. In fact, quite often the tendency to ruminate makes things worse. Part of my cognitive behavioral therapy has specifically focused on training myself to STOP ruminating all the time. And one of the first effects I noticed from taking anti-depressants was that the temptation to ruminate diminished. This has made it EASIER to function in society.

    In my view, whenever dealing with apparently pathological or antisocial behaviors (depression, rape, self-harm, infanticide, ADHD, etc.), the null hypothesis should always be that they are a non-adaptive byproduct of our normal cognitive adaptations to social life. Anyone wishing to argue that these psychological aberrations are adaptations needs to refute the byproduct explanation first. I’ve heard lots of arguments that various apparent disorders are actually adaptations, and they usually range from somewhat plausible to wholly preposterous.

  13. “it’s hardly ever the case that these ruminations are productive. In fact, quite often the tendency to ruminate makes things worse.”

    That’s the assumption I’ve been going on. Because the ruminations of depressed people are depressive. You have to be not depressed to have productive ruminations.

    That’s even true of sleep deprivation – it distorts your mood and that distorts your thinking. I belatedly figured this out some time in my 20s, because I would take overnight plane or ferry trips and then find myself in a pit of despair the next day. It finally dawned on me that the mood wasn’t ‘real,’ it was just lack of sleep (duh), so after that I knew to ignore any conclusions I came to after being awake all night.

  14. As someone who’s suffered from depression (and not found drugs useful) I can’t stress enough that it doesn’t lead to useful thoughts. It leads to self-destructive, hateful, futile thoughts, and the idea that these confer some evolutionary advantage is absurd. A little melancholy rumination – like Gray in his country churchyard – is nothing like true depressive illness.

  15. A late comment on Professor Coyne’s incisive posts on the Analytical Rumination Hypothesis of depression:Some of those who commented on the post seem to have accepted the serotonin hypothesis of depression. I advise them to read the article by Lacasse and Leo published online in PLOS Medicine on 08 Nov 2005.

  16. Good discussion overall, but I think you are a bit too dismissive of the hypothesis that difficult situations cause depression. What of all the classic studies from Camberwell in the 70s, replicated many times since, which demonstrate that negative life events are major risk factors for the development of depression?

  17. No.
    Just no.
    Sorry for the authors of this article, nice try, but they are totally wrong.
    And it is so simply to prove they are wrong: there can be rumination without depression. Period.
    It’s a fact that rumination indeed is a way to focus on problems.
    It’s a fact that rumination indeed prevents you from eating, enjoying other activities, etc.
    It’s a fact that rumination indeed is triggered by social problems (other kind of problems, eg survival problems are less likely to trigger rumination, they more likely trigger action).
    On the other hand:
    It’s a fact that depression indeed can be triggered by social problems.
    It’s a fact that depression indeed prevents you from eating, enjoying other activities, etc.

    These facts mean that depression has something to do with rumination, because they share some characteristics? It’s a total mistake.
    Being worried about something is not being depressed.

    Depressive rumination is ALOT different than problem solving rumination.

    Besides rumination exists extensively in OCD and probably in other mental disorders with no comorbid depression at all. Maybe this means that OCD is adaptation too? This is ridiculous!

    Depression is not always caused by social problems.
    Depression distorts perception and makes you think you have problems or at least magnifies the small problems you have (eg depressed people feel guilty without reason).
    Thus, depression has nothing to do with problem solving.

    Human organism has other methods to induce and maintain rumination, that don’t need to alter mood. For example dopamine does this quite good, it offers idea creation as well!

    As for the experiment that some people who had sad mood did it better: they did it better because they wanted to run away! Their mood was ‘dislike’ not ‘depression’. If they were really depressed they would feel helpless and hopeless!

    Depression has NO role in human’s life, it is a nature’s problem, and simply not everything in nature is ok.

    Two similar feelings may have an evolutionary role, but must not be confused with depression:
    Grief over a loss is much different than depression. The quality and quantity and characteristics of these two feelings are totally different. It is just that for many people, they trigger a major depressive episode, so psychologists cannot distinguish them.
    Empathy has nothing to do with depression. The feelings are different, probably processed by different parts of the brain. Empathy may promote social bonding, but depression is absolutely unecessary.

    Many species live, function, form families and societies, without experiencing grief. Grief and sadness, depression even more, are not needed.

Leave a Reply