A friend sent me this New York Times story called Depression’s Upside and my reply email ended up getting long enough I thought I’d blog it. The primary academic source is this interesting article in Psychological Review which also got coverage in Newsweek last year.
The superficial summary is that depression is an evolutionary adaptation, and that is still helping us solve problems in modern society. Is this true? These are two very distinct claims and while each may have some merit, saying it like that may obscure as much as it enlightens. These are not completely novel ideas, and the authors of the original article, Andrews and Thomson, discuss an enormous amount of relevant research. I learned a great deal reading it but I was troubled that they downplay the distinction between low and high levels of depression. Andrews and Thomson justify this in the following paragraph:
It is not uncommon to see arguments that depression might be adaptive at low levels but is maladaptive at levels that reach DSM criteria (Dobson & Pusch, 1995; P. Gilbert & Allan, 1998; L. Lee, Harkness, Sabbagh, & Jacobson, 2005; Markman & Miller, 2006; Nettle, 2004; Price et al., 1994; Wolpert, 2008). These arguments implicitly assume that clinical and subclinical episodes are qualitatively different. (624)
But that isn’t really true in any meaningful sense. Yes, major depressive disorder appears to be the tail end of a continuous distribution of symptoms that we all experience. (Does this remind you of my discussion of social class?) But this does not invalidate other scholars claims that depressive symptoms may be adaptive at low levels and maladaptive at high levels. To be more precise, it is not depressive symptoms which might be adaptive, but the predisposition to depressive symptoms when faced with particular circumstances. They go on to say:
Because we think that the clinical significance criterion leads to the overdiagnosis of depressive disorder, we intend our arguments to apply to a range of depressive symptoms, from transient sadness to much of what would currently satisfy DSM–IV–TR criteria for major depression. (624)
Clinical depression may be diagnosed, but that is not a logical justification for assuming the whole range of symptoms can be lumped together when addressing various issues, e.g. whether depressive symptoms have adaptive value. There is no doubt in my mind that our brains social and emotional processing systems were shaped by natural selection. There is a sense in which our predisposition to react to particular situations with depressive symptoms must have been an adaptation. But severe depression is obviously not an adaptation. Adaptations increase inclusive fitness; severe depression does not. Frankly, I think Andrews and Thomson are negligent in not pointing this out. In failing to discuss it, they lend sympathy and comfort to those who would argue that even severe depression is a morally or medically necessary state that people need to “earn” their way out of.
Another idea Andrews and Thomson spill too little ink on, is that severe depression could be the result of a mismatch between the environment our brains evolved for, and the modern environment we have created. This is the same logic behind why we instinctively eat more fat and sugar than is good for us. One of the ways to test this is to estimate the prevalence of severe depression among hunter-gatherers. Though at least one scholar (Ness) has argued it is far lower, but my googling wasn’t able to find strong evidence for or against this claim. I can recommend another review article which focuses on the broader issue of how mental disorders could have evolved.
When I was reading all this I identified a few questions I thought might clarify the issues:
Do people on a semi or fully unconscious level choose depression because it helps them achieve certain goals?
Well, if its an unconscious decision, then in a sense, evolution chose it… a huge amount of our behavior is best understood as unconscious, but the word choice is probably misleading in this circumstance. I think it is usefully descriptive to say that some people semi-consciously choose depression, but that is only because their other options appear (to them) even worse, e.g. giving up deeply held values.
Accepting that depression can on some level be understood as assisting in the achievement of certain goals. To what extent are those goals aligned with maximizing inclusive genetic fitness?
Very little for most people in modern society, perhaps (speculation) more in the environment of evolutionary adaptedness.
How should an individual or society weigh the goals depression helps achieve and other alternative goals, e.g. not being depressed?
I don’t have a good answer for this and would be skeptical of anyone who was highly confident of their own answer. That said, I think it is fair to say that most cases of depression have little redeeming value. So it seems reasonable to want to reduce depression and to be willing to consider pharmaceutical approaches. On the other hand, their track record is extremely spotty. I know that some researchers have claimed that physical exercise and some forms of therapy are as effective as drugs. I expect that fifty years from now we will look back on how we’re treating depression and conclude that we were doing it wrong (not that we will have discovered the perfect treatment). But that’s life, we have to make choices today with our very incomplete understanding of the world.
One final note, I noticed I found myself writing about “depressive symptoms,” rather than “depression.” Psychiatric diagnoses, including depression, are not particularly well defined. On the one hand, we all use the term depression because it communicates something, on the other hand it conceals a lot of complexity that psychiatrists don’t understand very well… it would often be helpful if researchers would focus on something more fine-grained, i.e. clusters of symptoms.
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 DOI: 10.1037/a0016242
Permutations 
HI. I agree that it can be hard to find the answers that are wanted due to the lack of understanding of this disease. However we are entitled to opinion, and given the facts available, I personally do not see the upside of depression, nor the evolutionary purpose. I believe this because of the rate of suicide linked with depression, as well as the common lack of productivity by sufferers.
That being said, some of the great minds in history suffered from equally understood mental diseases. Abraham Lincoln suffered from depression, Nikola Tesla suffered from OCD etc. I would be interested to see enough data to support that depression has some sort of advantage to us.
There is no doubt in my mind that our brains social and emotional processing systems were shaped by natural selection. There is a sense in which our predisposition to react to particular situations with depressive symptoms must have been an adaptation.
This is one of those common evol-psych conclusions that I just don’t buy. Everything humans do / experience does not have to be adaptive — it merely has to not kill us (or make us incapable of reproducing). Depressive symptoms don’t have to be adaptive, positive, etc. They must merely fail to be bad enough.
I wrote a poem when I was ten or eleven about how negative emotions make positive emotions even better, and as this article points out, artists a lot awesomer than my ten-year-old self have been doing the same forever. Frankly, I don’t see anything in this article that’s much more convincing than the artists. Your questions are much more interesting than the article, and much more interesting than the artists for that matter, and I think that part of the reason the article avoided them is that they’re also much harder and politically difficult. People are very likely to read question 1, for example, as blaming the victim.
P.S. I wouldn’t be surprised if hunter-gatherers had lower incidence of depression, but I also wouldn’t be surprised if stigma in resource-poor societies was much less conducive to depressives coming out, and/or if such societies lacked cultural resources to assist depressives in articulating their feelings. I have heard from anthropologists that resource-poor societies also appear to contain fewer sexually non-normative people — this doesn’t necessarily mean that those people don’t exist there; merely that they lack the personal or psychological space to express their differences.
Clarisse, regarding the two sentences you quoted… depressive symptoms, in the broadest sense, which is what the academic article was often referring to, include simply the capacity for sadness, loneliness, anxiety. These basic emotions which are to a significant extent universal, are as much subject to natural selection as the design of our visual system. Is the functioning of these basic emotions interact with feedback from the environment including culture? Absolutely, and (perhaps to a lesser extent) so does our visual system and our immune system. Given that evolution invented the eye between 50 and 100 times and could plausibly design it from scratch in 400,000 years, don’t you think it is capable of a fair bit of fine-tuning of our emotions?
Our understanding of emotions will be missing something incredibly important if we fail to recognize and synthesize the insights from evolutionary psychology about adaptations, in addition to insights from neuroscience about brain activity in real time, insights from pharmaceutical psychiatry about how drugs affect emotions, insights from psychology studying individuals emotions in detail, and insights from sociology studying how emotions vary across individuals based on their social roles, and the culture they belong to.
I said, “there is a sense in which… [emotions] must have been an adaptation” because I realize this can be interpreted differently and it is difficult to be more precise. No biological, psychological, or societal feature is adaptive when removed from context. All adaptations are compromises, there are serious design constraints, many different types of tradeoffs. Though I think I’m communicating something important when I say: “Sadness as a response to social rejection evolved to discourage people from doing things that get them socially rejected, because those who are socially rejected have fewer successful offspring.” But I felt like focusing on the negative I could say, “Sadness is a blunt, highly imperfect emotion which fails in x, y, and z. It exists as a side effect of these other things.” So to a certain extent whether something is an adaptation or not depends on your perspective. But nonetheless, I think we can fairly clearly state some things are far more “adaptationy” than other things.
I hope that my analysis in this post doesn’t sound callous, and I hope that the people who know me think I am understanding and respectful in my actual behavior and interactions with people suffering from depression. I also hope that people will let me know if they find my writing insensitive. Another thing I could have emphasized more is the is/ought fallacy. Even if something is adaptive, that doesn’t make it “good” in a moral sense.
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Do people on a semi or fully unconscious level choose depression because it helps them achieve certain goals?
Many people look back at their struggles in life and see that through those struggles they have overcome and actually benefited. But say that people choose those struggles? For those of you who are older, Chuck Colson fell from the top to be in prison. From there he started a great organization, Prison Fellowship. Although his fall from grace and his time in prison lead to great things, I don’t believe one could conclude that Mr. Colson choose such a path.
It seems silly to think that anyone would choose depression.