I want to draw an analogy with fever. Fever is a "rational" (that is, both effective, and intended) response of the body to infection. The body raises the set point of its thermostat, because the invading bugs are less able to survive the elevated temperature than the organism that they are trying to invade.
But you can still die of a fever.
However, what I have read of depression (of which I have no personal experience) suggests that if their "ecological" hypothesis is true, clinical depression is analogous not to fever in general, but to the end stages of a failed fever defence -- not simply an adaptive response to stress, but the defeat of that response by the magnitude of the stress, and the collateral damage.
The journal article is available at the usual place: use the scientific articles field and search by the DOI.
Thanks, I didn't know about that place. I hesitate to link to it, since it may be unauthorized and linking to unauthorized reproductions can get one into trouble in U.S. law. But I will add the doi to my post, which could help people with many ways of searching besides this one.
Depression seems to me to be similar to hibernation rather than some sort of better-processing state. Social Isolation, the depths of winter, and lack of meaningful tasks in life seem to be the situations where becoming tired, slow to act, and pessimistic are adaptive. If you're living through the winter in a cave off mammoth jerky, it's probably better to get depressed than to go stir-crazy. If you have plenty of food and no pressing tasks, you'll probably live longer if you can't get up the energy to get out of your house.
As a comparison, consider the effects of a surge of Adrenaline: Higher function, faster thinking, stronger muscles, and insensitivity to pain. You're more willing to take risks and tire yourself out.
The key difference seems to be urgency: depression might be a chemical state that you go into when you're in a situation where urgent action is bad, and "fight or flight" when urgent action is necessary.
So how does suicidal ideaton fit with this? Is the benefit of hibernation that much higher than the probability of killing oneself? Also why does being depressed feel miserable then, sleeping for example is a very enjoyable experience, at least for me.
Side effects: Our brains are machines that sometimes have very crude control mechanisms. Floods of certain neurotransmitters to enrage us, others to make us feel love and lust. The sort of chemical conditions necessary to encourage torpor and cautious behavior also make us "sad".
Some thoughts on the topic. My initial view of depression has been that it's an evolutionary thing that does something beneficial socially. Once the environment has changed considerably, this response does not work to one's favor anymore. So that has been how I view it. I read the wikipedia's hypotheses from MarkL's link and I think all of them made a lot of sense. Essentially my predisposition was that of "Possibilities of depression as dysregulated adaptation".
What seems to be missing from the discussion is the order in which things evolve. For an example the theory on that wikipedia page about prevention of infection does make sense, from the perspective of if someone close to the person passes away from a disease then it might be a good trigger for timing a preparation sequence for infection. But then on the otherhand for this to make sense it would probably have to take place in a social environment, if the very closest person to you in a non-social environment would have this happen, then perhaps the timing of the depression to guard against infection would be off.
I suppose the wikipedia page contemplates on this issue from a general means of avoiding infection, which I think is a pretty questionable hypothesis. Would seem like general depression is not a good state to maintain, or activate randomly for long periods of time, and I think it would require a trigger or a timing to be logical from the adaptation perspective.
Analytical rumination seems really interesting. I think that makes sense on many levels, reconsidering what you're doing, as well as avoiding activity before engaging with problems. To get slightly depressed every now and then might result into optimization of behavior or more accurate refinement of goals by temporarily increasing reflective behavior and downregulation of activity and intensity of goal oriented behavior. So whenever there is a drastic depressive change then it would make sense to go things over again.
I think the honest signaling theory is really interesting too, but I think of that as a component to signalling in general, all strong signals could be argued to benefit from honesty, and only after the honestiness of signaling has altered the environment, dishonest signaling becomes advantageous. I think of that kind of stuff in the following terms: First a system needs to evolve succesfully before some other system can develop a parasitic relationship to it. In otherwords you wouldn't have dishonest signaling before a system of signaling is in place, all signaling has to be honest before some of it can be dishonest. But these signals on the otherhand have much longer history than humans do, so it's pretty hard to pin point what happened and when.
Behavioral shutdown model makes a lot of sense from the same perspective as analytical rumination. Losing interest in current goals and patterns due to failure, and going into a waiting mode to find new goals.
If depression would be viewed as a quantitative effect on behavior, then you could also see it as a mechanism of improving the individuals ability to optimize for behavior's rewards:stress ratio. So if you be inclined to do very stressful things due to the way you were brought up or by some individual characteristic, and in return you would have very low gain, then it would make sense for there to be a system inplace which corrects you behavior and optimizes rewards:stress ratio of you behavior.
So with that particular way of phrasing the shutdown model it essentially becomes the psychic pain hypotheses, both have the same purpose. However psychic pain hypothesis adds something to it, the idea of seeing the depressed state as unwanted state and things that cause it as something to be avoided.
Rank theory seems also very interesting. However is that a special case of behavioral shutdown model, or is a generic phenomenom of it's own? To put it in other words.. Let's say an individual is striving towards leadership of the tribe, and keeps failing. It would make sense that these attempts could be very costly and the returns could be very low, and backing off and giving those plans attempts could result to more efficient behavior. So in that case it would be the behavioral shutdown and psychic pain combined. But the rank theory does add it's own component, which the ranks, steering towards a role more suitable for the rank. I can't see why this behavior pattern couldn't be dynamic and function in both circumstances.
I think the social risk hypothesis is very close to the rank hypothesis.
I think depression also signals genuine relationships between people, from the honest signaling perspective. How would the other members of the tribe react to somebody who had a long lasting relationship with someone, and then they wouldn't mourn for that person at all - wouldn't really be affected at all? How would that be met? Would that kind of person be trustworthy at all? People who have strong bonds would be willing to go to amazing lengths to save their friends. Cetrainly you can't be a person like that, if you're not even touched by losing someone close to you. So I think that does have to do with depression.
Personally I think depression is largely about the society growing too big. If people get depressed here they can be left outside the society, and they're not involved with the society on an emotional level which involves communities, relationships, but instead are just sort of interacting only on the surface of the society, not being really involved with anyone.
In a smaller tribal community this apathetic withdrawal behavior probably wouldn't work like it does in the modern individualistically secular society. Where as in the modern society a valuable member of tribe can be forgotten inside her single room apartment, I don't think that would happen in a tribe of 80 hunter gatherers. As humans are capable of being sympathetic, you might not starve all that easily, and perhaps other people would be interested in why you're in your depressive state, and perhaps that would lead to forming new relationships and losing the depression. There would be duties to do.
So I think depression can also be a result of social deprivation, and in a different circumstance the behavior might result to new relationships being formed. While in the real world, psychiatrists, people you mee on street, cashiers in shops your co-workers, perhaps even friends, might not form a real relationship with you. You could just be on surface, acting along these wordly guidelines and ideas of how an individual is supposed to exist. This has very tragic implications if these people are then directed to interact with individuals who most certainly can't form real relationships due to their professional ethics. It's pretty common that the patients can form strong attraction or bond to the their nurse or shrink. Everybody can be phony, people wear their faces like masks on their jobs, they restrict from expressing their real emotions, they cocoon inside their shells and on the outside they're like an illusion. Friendships and relationships that real are really important to people emotionally. It's important to form bonds and have a feeling of community. In a sense the business world has ruined it all. We're co-operating social people but the way you've to do that co-operation is now harnessed by this system of selfishness and cruel deception. Even loved ones can be very treacherous and negligent towards their partners, building up some superficial idea of what an individual's conjunctionally possessed partnership is about.
The idea is a variation on one that's somewhat popular here: that some conditions usually regarded as mental illnesses (Asperger's for example) are beneficial, even adaptive.
I have a hypothesis that autism-spectrum conditions are less selected against and therefore proliferate as a result of increased background levels of literacy (increasing the amount of information you can acquire without direct interpersonal teaching). I haven't maintained enough interest in this hypothesis to see if there are any natural experiments to look at.
If that were true, I would expect that depression would make you creative, so you could think of creative solutions to your problems. My experience suggests the opposite of this post... when I had a big problem in my life and became depressed about it, I believe that depression made solving the problem significantly harder. In order to solve my problem, I needed to try many different things, none of which had a high probability of working. Depression made me pessimistic that any of them would work, so I was not that motivated.
This bothers me too. In my own experiences with depression, it certainly led to rumination, but not particularly useful rumination. Mostly the same thoughts over and over, and mostly unhelpful ones to boot. (Edit: typo.)
Labeling the phenomena depression frames the debate in a certain way, that's not useful for understanding evolutionary reasons.
If you hit someone strongly on the head the resulting trauma can frequently lead to depression. Is that depression in reaction to getting hid on the head evolutionary advantageous? That depends highly on how you have to structure a brain to not suffer depression when it get's hit.
While Googling around it seems that dogs also have something like depression: http://pets.webmd.com/dogs/features/depression-in-dogs Does depression helps dogs to solve complex problems which involve analysis? Is that what Andrews et al are arguing?
More evolutionary perspectives here:
http://en.wikipedia.org/wiki/Evolutionary_approaches_to_depression
If that were true, psychotherapy (especially psychotherapy focused on the patient's relationships) would always work. (Incidentally, at least on the authors is a psychiatrist in private practice, who would want to believe that.) That isn't the case.
I think the rank theory of depression, while similarly characterized by evolutionary/speculative reasoning, makes a lot more sense.
Something having evolved because it's adaptive in the cases when it's temporary doesn't mean that trying to treat its non-temporary manifestations would always work. The mechanism that was normally supposed to bring us out of depression could be broken.
The mechanism that prevents other people from denegrating someone who already looks downcast could break too.
Psychotherapy wouldn't work if working with the psychotherapist didn't elicit a workable solution. I've intermittently found psychotherapy to be very helpful, but it doesn't always solve the problem for which I went to psychotherapy for.
Could it somehow be both? Maybe if you have lower status, solving complex problems becomes relatively more important, because you have less alternative opportunities. For higher-status people, even when they are capable of solving problems, letting other people solve problems and just taking their stuff is probably more profitable. Losing status could imply that you should switch to problem-solving mode, because that's the way to be useful to your new masters (and your quality of life now depends on their opinions).
This would seem to be supported by the fact that sad moods make us process information more analytically.
In addition to providing information that can serve as a basis of judgment, feelings influence how people process information, that is, their processing style. A number of different explanations have been offered for this observation, usually highlighting the role of one specific type of feeling (for reviews see Schwarz & Clore, 2007, and the contributions in Martin & Clore, 2001). Feelings-as-information theory provides a unified conceptualization of these influences in the context of a situated cognition framework (Smith & Semin, 2004). It assumes that human cognition stands in the service of action (James, 1890) and that our cognitive processes are responsive to the environment in which we pursue our goals. This responsiveness ranges from the higher accessibility of knowledge relevant to the current situation (e.g., Yeh & Barsalou, 2006) to the choice of processing strategies that meet situational requirements (e.g., Wegner & Vallacher, 1986). When things go smoothly and we face no hurdles in the pursuit of our goals, we are likely to rely on our pre-existing knowledge structures and routines, which served us well in the past. Moreover, we may be willing to take some risk in exploring novel solutions. Once things go wrong, we abandon reliance on our usual routines and focus on the specifics at hand to determine what went wrong and what can be done about it. [...]
The theory further predicts that feelings or environmental cues that signal a “problematic” situation foster an analytic, bottom-up processing style with considerable attention to details, whereas feelings or environmental cues that signal a “benign” situation allow for a less effortful, top-down processing style and the exploration of novel (and potentially risky) solutions (Schwarz, 1990, 2002). This does not imply that people in a happy mood, for example, are unable or unwilling to engage in analytic processing (in contrast to what an earlier version of the theory suggested; Schwarz & Bless, 1991). Instead, it merely implies that happy feelings (and other “benign” signals) do not convey a need to do so; when task demands or current goals require bottom-up processing, happy individuals are able and willing to engage in it. A study that addressed the influence of moods on people’s reliance on scripts (Schank & Abelson, 1977) illustrates this point.
Employing a dual-task paradigm, Bless, Clore, et al. (1996) had participants listen to a tape-recorded restaurant story that contained script consistent and script inconsistent information. While listening to the story, participants also worked on a concentration test that required detailoriented processing; in contrast, the restaurant story could be understood by engaging either in script-driven top-down processing or in data-driven bottom-up processing. Happy participants relied on the script, as indicated by the classic pattern of schema guided memory: they were likely to recognize previously heard script-inconsistent information, but also showed high rates of intrusion errors in form of erroneous recognition of script-consistent information. Neither of these effects was obtained for sad participants, indicating that they were less likely to draw on the script to begin with. Given that top-down processing is less taxing than bottom-up processing, we may further expect that happy participants’ reliance on the script allows them to do better on a secondary task. Confirming this prediction, happy participants outperformed sad participants on the concentration test. In combination, these findings indicate that moods influence the spontaneously adopted processing style under conditions where different processing styles are compatible with the individual's goals and task demands, as was the case for comprehending the restaurant story. Under these conditions, sad individuals are likely to spontaneously adopt a systematic, bottom-up strategy, whereas happy individuals rely on a less effortful top-down strategy. But when task demands (like a concentration test) or explicit instructions (e.g., Bless et al.,1990) require detail-oriented processing, happy individuals are able and willing to engage in the effort.
Numerous findings pertaining to a broad range of feelings (from moods and emotions to bodily experiences and processing fluency) and cognitive tasks (from creative and analytic problem solving to persuasion and stereotyping) are consistent with the predictions of feelings-asinformation theory (for reviews see Schwarz, 2002; Schwarz & Clore, 2007).
Well, I haven't really thought about it, but what first comes to mind when thinking of prehistoric humans vs modern people, is that they were "tough" because their life was very hard, and we're quite "wimpy" because our lives aren't. The worst that can happen to modern people, and the worst that can happen to cavemen, are pretty much the same thing, but our overall lives are far easier and so there's much more contrast.
Perhaps it is a neurological response that causes debilitating disorder to modern people, but which merely made cavemen a little wary of going outside for non-essentials.
This seems like it should be testable. There may be no cavemen around, but there are still uncontacted and recently-contacted tribes, as well as whole countries where life is far harder than ours. I wonder what the statistics look like for those..
There are many facets to depression and to analyse them from a evolutionary perspective, you should evaluate every single one them separately.
Some specific types of depression, like 'burn-out' syndrome, have an obvious cause-effect and is some sort of defense mechanism to protect you from yourself. The metaphor of getting burned is fitting, because it's similar to physical pain.
But evolution doesn't bother if something is beneficial or not. A common mutation can be devastating for the individuals mental health, but as a species we can have evolved to circumvent this weakness by triggering certain behaviors to prevent us from reproducing. The courting behavior in animals is also often a test the behavior of a potential partner; unexpected behavior leads to rejection.
Genes do not evolve into cleaner, more efficient code, but rather into super complex buggy spaghetti-code that somehow works. We may have evolved to be somewhat intelligent, but we are also inherently flawed.
An interesting observation in that regard was the deranged penguin (documentary: Encounters at the End of the World).
Since there are intelligent people here who follow the topic of evolutionary psychology, I'd like to hear opinions about some research from 2009. Particularly if this idea seems reasonable or not, but possibly other opinions that people might have about it.
The idea is a variation on one that's somewhat popular here: that some conditions usually regarded as mental illnesses (Asperger's for example) are beneficial, even adaptive. But the condition in question now is depression. Briefly, the argument is that depression, at least when it is a response to stimuli and not a permanent feature, can have the useful effect of encouraging more rational thought when this is particularly important, even at the cost of quality of life, and that this is adaptive.
Links: a Scientific American article, a journal article (which I haven't read, behind a $12 paywall). Here's the abstract of the journal article:
The full journal citation is Andrews, Paul W., and Thomson Jr., J. Anderson; July 2009; Psychological Review 116 (3), 620–654; doi 10.1037/a0016242.