“Pain or suffering of any kind, if long continued,
causes depression and lessens the power of
action; yet it is well adapted to make a
creature guard itself against any great or
The Life and Letters of Charles Darwin,
Charles Darwin, 1887
This is a bit of a dangerous post, but so is depression.
The post is largely based on Nesse 2000, ‘Is Depression an Adaptation?’, which I heavily quote from.
Take home message if you don’t have time to read all the article:
Some negative and passive aspects of depression may be
useful because they inhibit dangerous or wasteful actions in situations
characterized by committed pursuit of an unreachable goal,
temptations to challenge authority, insufficient internal reserves to allow
action without damage, or lack of a viable life strategy.
Though, the author also points out that many depressions are disease states - so the notion that depression is an adaptive response might only be a subset of the range of potential depressions.
Continue to read to learn the more fleshed out idea:
I think most of us can agree that depression causes an immense level of suffering, for the person undergoing to depression, but also for the rest of the people close to the depressed. However, with such a large percentage of the population (see depression’s cost to the individual and society) experiencing this malady one might wonder if depression has a ‘function’. And this point Darwin was trying to convey in the opening quote of this piece.
Okay, if we are going to entertain this notion we must still wonder what could possibly( be the function of depression?
Nesse, offers a number of possibilities but emphasizes the idea that depression may play a role in drastically reducing motivation for unreachable goals.
If a commitment to pursue a goal encounters an obstacle, efforts increase and become aggressive. If the obstacle cannot be overcome, low mood helps to disengage the commitment
and end the cycle. If the individual cannot disengage, low mood escalates. Klinger concludes, “depression is ordinarily, therefore, a normal, adaptive part of disengaging oneself from an incentive.”56(p21).
If failure to reach a goal might induce depression to ‘encourage’ the organism to stop pursuing a particular goal (that is unobtainable), then one might surmise that those seeking the highest goals might suffer more depression in an attempt by the system to alter the pursuit of lofty goals.
Clinicians have long noted that depression is common in people who
are pursuing unreachable goals.47,48 “Failure to yield” may be an example,
in the status competition domain, of this more general situation.
When current life plans are not working, the distress and lack of motivation
that characterize depression may motivate planning and reassessment49
or escape, even by suicide.50
To bring in some neuroeconomic aspects to shine light on this problem one needs to think of the commitment of resources (time and energy) in pursuit of a goal with payoff X. Obviously the loftier the goal the greater potential reward, but also the probability is lower. However, if feedback with the environment is indicating that this goal is unobtainable for a particular individual there is a need for a signal to stop pursuing this ‘unprofitable’ wager.
In the article Nesse quotes Wender and Klein:
. . . biologically based self-esteem— and mood in general—seems to us to
have evolutionary utility . . . If one is subject to a series of defeats, it pays to
adopt a conservative game plan of sitting back and waiting and letting others
take the risks. Such waiting would be fostered by a pessimistic outlook.
Similarly if one is raking in the chips of life, it pays to adopt an expansive risk
taking approach, and thus maximize access to scarce resources.73(p204)
This starts becoming interesting and I would like to refer you to a couple articles I have written about optimism and hope (The neuroscience of hope, optimism is good for your health, is the glass half full or half empty: rACC brain activation, are organisms by nature optimists?).
This line of thinking suggests that depending on your probability of success one needs to appropriately adjust your ratio of optimism/pessimism. Of course this just makes common sense that we adjust our behavior based on probability of success, however the question is does depression play a role in adjusting your ‘attitude’, your goals?
Going back to Darwin, one needs to think of how something that seems so hideous like depression would actually improve ‘fitness’ (fitness defined as reproductive success - passing on the genes). If depression reduces the pursuit of an unobtainable goal, and forces a reassessment of the persons overall situation, and an eventual choosing of a goal that will result in a payoff then this could increase the person’s fitness level - then maybe depression could improve the individuals fitness.
I will give an example. Take a 21 year old person who moves to Paris (or Prague, etc) to become an artist (just to take a well know dream/pursuit) for that is their passion. They have an incredible level of drive and determination. This person does whatever is needed to pursue their goal of becoming an artist. Of course it is difficult, as is becoming an actor, athlete, etc. Despite the dogged determination this person has had very little success when nearing their 29th birthday. They might continue to pursue their goal, supplementing their income with low-income, temporary work like they have been doing for the last 8 years. But their reproductive fitness in the culture is low - they are not considered a ‘good catch’ due to the uncertainty of their future, and total lack of success (money or otherwise). Now if the person becomes depressed because of their lack of success and lose all motivation to create their art, this might induce them to give up on their dream. Having abandoned their dream they start a normal job, say based somewhat on their background, as a graphic designer for computer games. The person doesn’t consider themselves an artist for they do not get to draw what they want, but instead what they are told. But the person becomes gainfully employed and his reproductive fitness increases.
However, since depression inhibits all activity then it might just contribute the person to staying in their current situation. If you are stuck in a well and depressed then you don’t have the mental energy to attempt climbing out. This would be a bit of a paradox to the potential adaptive advantage of depression. Nesse then argues that a quick dropping of a dream and a mad rush of to a new un-thought out pursuit would also be disadvantageous.
When depression is instead seen as a state shaped to cope with unpropitious
situations, it is clear how it could be useful, both to decrease investment
in the current unsatisfying life enterprise and also to prevent
the premature pursuit of alternatives. Failure to disengage can
cause depression, and depression can make it harder to disengage. This
may explain why the low-mood system is so prone to getting stuck in
positive feedback loops.88-91 Mood dysregulation may now be so prevalent
because we are bereft of kin, beliefs, and rituals that routinely extracted
our ancestors from such cycles.92
Nesse suggests that he conundrum of depression resulting from failure in life is resolved by accepting the reality of the individual’s life situation. And then the person moves on by giving up on the unlikely probability of their former goal. How this exactly happens was less clear to me. However, what was clear is that if the person fails to disengage then ‘serious pathology‘ is likely to occur.
Earlier in Nesse article he uses the example of an animal behavioral choices while foraging a food patch.
As the food in a patch is depleted, organisms give up on that patch at close to
the optimal time, namely, when the rate of return in the current patch declines
below the average rate of return over all patches. If the overall
rate of return from all patches drops below the cost, foraging stops.
Nesse then returns to this theme when discussing the neuroeconomics of the choice of people when it is apparent they need to move on. Changing your goal engagement is considerably more difficult than simply jumping to the next food patch because of the emotional investment in these various goals.
At least as important as the risks and costs of making a
change is the threat to the person’s identity, reputation, and sense of a
secure place in a social network and the cosmos.
At the end of his paper Nesse offers a few testable hypotheses, which are interesting.
The simplest untested prediction is that depression should be
common in people who are unable to disengage from unreachable goals.
Graduate students who are failing and faculty who are unlikely to make
tenure are obvious candidates for study, but other situations are far
more common: unrequited love, inability to get work, pursuing an elusive
large life goal….
Ability to repress such wishes should prevent depression.
Finally, Nesse wonders about the possibility that foraging/feeding patterns may be linked with the behavior of depression.
If the brain mechanisms that regulate foraging are related to those that mediate depression, then antidepressants should change the duration of foraging time in a depleted patch and the willingness to exert effort even when the net rate of return is negative. They might also change preferences for working hard for a large intermittent reward vs easily getting small, frequent rewards. If low mood is an active coordinated state, then the brain mechanisms that mediate it can be blocked at different points, so antidepressants should be effective via multiple mechanisms.
I find this last point particularly intriguing as I have written previously about the relationship between antidepressants and antipsychotic use, increase levels of ghrelin, and subsequent weight gain.
Take home message:
I guess one needs to know when to hold them, and when to fold them. In specific situations depression may be a signal emanating from your system to give up. The trick is not to give up on life, but rather only give up on the specific unobtainable goal. But on the other side of the coin, ‘what if life without a dream’.
I do not know if a subset of depressions is an evolved adaptive response to stop us from chasing after fruitless endeavors (empty food patches), but it does provide food for thought.
(some of Nesse’s followup papers: Nesse 2004, Keller and Nesse, 2005, Keller and Nesse 2006, Nesse and Ellsworth 2009.)